# Corydoras in hard water...



## Fabio Perini

Hi All,

Just wondering if you would consider silly keeping Corydoras Panda in hard water (PH 7.6, GH 13, KH 9). I was thinking of keeping them with Cherry Barbs.
I'm not sure I want to get into the slavery of RO for a bigger tank as I already have one using it and I find having to go to the LFS and pay £3.50 for 25 litre is okay when it lasts you more or less a month for a 30 litre cube but quite doubtful in case of a much bigger tank.
I know I could go for hard water fish but I really like catfish...
Thoughts please?
Cheers,
Fabio


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## tam

That's not super hard, unless you are trying to breed them, I'd have thought they'd be fine. Buy them locally and they'll be living in your local tap already.


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## Conort2

They'll be fine. I've kept and successfully bred wild caught corydoras metae in london tap water which is rock hard. Corydoras panda will more than likely be tank bred so should be even easier to keep and breed.

Cheers

Conor


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## alto

One consideration with Panda Cory’s - even tank bred seem to prefer lower temperatures



> 72 to 77°F (22 to 25°C


Seriously Fish


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## sparkyweasel

Cherry Barbs like the cooler end of the tropical temperatures too, so no problem there. Were you thinking of any more fish species, or just the two?
Maybe danios to occupy the upper levels?  They will do well at lowish temps as well.


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## Fabio Perini

All,

Thanks very much for your kind messages!

I'm an avid reader of most publications and websites like Seriously which is my go-to source to see whether a fish is suitable or not. However, even on Seriously at times, I can't understand the logic. For example, if you look at Paleatus it suggests a tank size which seems too small for them, not sure if it's just a typo or what.

My tank is not ideal for Corys as the footprint is 24"x12" but it's 18" high, at the moment that's what I've got and probably will upgrade to something different in the near future. Hence the Panda. Planning to keep the tank at 22 degrees which should be okay for both Panda and Cherry. What stocking levels would you suggest? I was thinking 6 Corys and 6 Cherry... I would love to get something for the upper section of the tank but I'm worried about overstocking... I'm running a big TowerBlock filter from SwissTropicals 4"x4"x8" which will be more than capable to handle the waste but itself already takes quite a bit of space 

I have no intention of breeding them, I don't have the expertise or space. I just would like the fish to be healthy and hopefully live a decent life.

I even thought about mixing RO with tap but I'm not sure if it's a safe option.

I got Unipac Maui fine sand for them. Decent choice?

Many thanks again!

Cheers,
Fabio


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## tam

You could consider Habrosus - they are smaller. Then maybe 5/6 Ember Tetras or some chili rasbora.

You can mix RO and tap to soften slightly, but really no need.


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## mort

I keep panda and adolfoi cories in a 24x12" tank and they do well. They are a small species and I keep nearly all the substrate clear of decor, apart from some twigs and leat litter. I maintain a minimum temp of 22c and they breed without intervention. I do use partial RO for water changes but am slowly transitioning the tank to pure tap water (which is similar to yours) because it makes everything so much easier. Tank bred cories are pretty happy in anything.


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## dw1305

Hi all, 





Fabio Perini said:


> Corydoras Panda in hard water (PH 7.6, GH 13, KH 9).


I think they are fine in harder water. The tap water locally is about 17dKH, and I know a number of people who breed them in it. They don't like it too warm, but other than that they are pretty adaptable.

Fish from the Andean piedmont or Panatanal (S. or W. of the main Amazon basin) are usually OK in harder water, it is the ones from the central Amazon basin (Rio Negro drainage etc.) that need really soft water. 

cheers Darrel


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## Fabio Perini

dw1305 said:


> I think they are fine in harder water. The tap water locally is about 17dKH, and I know a number of people who breed them in it. They don't like it too warm, but other than that they are pretty adaptable.



Hi Darrel,

I have a question for you regarding the water supply. I was talking to the manager of the Waterlife shop in West Drayton and he said that due to the PH swings in their water supply they buffer the water to make it suitable to the fish they are selling, trying to reproduce the water parameters of the breeding farms. 
Now, the cynic in me thought he was trying to promote the Waterlife PH buffering product, and a very expensive too: 10 quid a pop to treat just 300 to 400 litres of water!
How much truth is there in the statement that the PH of the water supply swings significantly? And if there is some truth in it, how do we protect our fish when using tap water?

is 17dKH referring to my area? I couldn't really find the figure in the water quality report from Affinity, I guess you need to calculate that from other parameters.

This the summary of my supply zone...


*Water Supply Zone: Weybridge/Woodham (AF067) Period: 01-Jan-2017 to 31-Dec-2017*


*This information is taken from historic results of monitoring and may be subject to change. This information is provided as a guide only and is subject to our terms and conditions.


HARD WATER
The area supplied by Affinity Water has 'hard' water. The hardness occurs naturally and is characterised by the presence of high levels of calcium and magnesium, which are good for healthy teeth and bones.
CALCIUM 115 mg/l
Calcium is the principal constituent of hardness.
TOTAL HARDNESS 287.5 mg/l
Total hardness is usually expressed in terms of calcium carbonate and is measured in milligrammes per litre (mg/l) which is the same as parts per million (ppm). The recognised classification scheme we are using is: 0-75 soft, 76-150 moderately hard, 151-300 hard, 300+ very hard. Your water is hard.
Degrees English (or Clarke) 20.125
This hardness measurement is used on some British appliances.
Degrees German 16.1
This is used on some German appliances.
Degrees French 28.75
This is used on some French appliances.
MILLIMOLS 2.875 mmol/l
Millimols per litre. Some appliances refer to water hardness in millimols per litre (mmol/l).
FLUORIDE 0.152 mg/l
Fluoride naturally occurs in the water in many areas. Affinity Water does not add any fluoride to your water. Fluoride is measured in milligrammes per litre (mg/l).*

Thanks in advance for your time.

Cheers,
Fabio


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## Fabio Perini

mort said:


> I keep panda and adolfoi cories in a 24x12" tank and they do well. They are a small species and I keep nearly all the substrate clear of decor, apart from some twigs and leat litter. I maintain a minimum temp of 22c and they breed without intervention. I do use partial RO for water changes but am slowly transitioning the tank to pure tap water (which is similar to yours) because it makes everything so much easier. Tank bred cories are pretty happy in anything.



Hello Mort,

Thanks very much for the information which is quite comforting. How long have you been keeping the Panda and Adolfoi in the 24x12 tank? How many of them do you keep? Is it a Corys only tank? Out of curiosity, what do you do with the offspring?
When you say you do partial water changes with RO, were you doing a 50/50 split or different? Was the tank setup initially as tap only or did you have RO in it from the start?
I assume the tank to be planted?
Sorry for the many questions, just very interested in your setup.
Thanks in anticipation for the insight.
Cheers,
Fabio


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## Fabio Perini

tam said:


> You could consider Habrosus - they are smaller. Then maybe 5/6 Ember Tetras or some chili rasbora.



Hi Tam,

Thanks for that. 
I do like Habrosus and I will have a tank for them, however as they are wild caught I would use RO in that case. I already have Chili Rasboras in an extremely soft water tank with zero KH, buffered by Shirakura Bee Sand. They are doing fantastically well and their coloring is from another world! I doubt they would do as well in tap. They live with a colony of shrimp and they don't seem at all interested in eating the shrimplets considering the massive breeding that is happening in the tank. I do like Ember Tetra and surely they seem able to adapt to a huge range of parameters.
Cheers,
Fabio


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## tam

Fabio Perini said:


> How much truth is there in the statement that the PH of the water supply swings significantly? And if there is some truth in it, how do we protect our fish when using tap water?



It can appear to swing if you measure straight from the tap and after it has stood awhile. To do with the change in CO2 levels I think. In some areas water can come from different sources at different times so can have different parameters.


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## dw1305

Hi all, 





Fabio Perini said:


> I have a question for you regarding the water supply. I was talking to the manager of the Waterlife shop in West Drayton and he said that due to the PH swings in their water supply they buffer the water to make it suitable to the fish they are selling, trying to reproduce the water parameters of the breeding farms. Now, the cynic in me thought he was trying to promote the Waterlife PH buffering product, and a very expensive too: 10 quid a pop to treat just 300 to 400 litres of water!


I'm cynical too, and <"I have a real problem"> with a lot of the sellers of aquarium products, they sell cheap chemicals, at an enormous mark-up, to rectify problems that don't really exist. 

If you have hard tap water the pH will be fairly stable and about pH 7.8 - pH 8.2. This value is reached because it is the equilibrium pH value for the <"carbonate ~ CO2"> buffering system at ~400 ppm atmospheric CO2.

pH will show a diurnal rhythm in a planted tank (without added CO2). During the photo-period the plants are net oxygen producers and the water is depleted of CO2, and the pH will rise, during the night all the bioload is respiring, oxygen levels fall, CO2 levels rise and pH falls.

When you add CO2 you change the pH equilibrium point, so the pH is lower. I'm not a CO2 user, but those who are will tell you that a fairly rapid change of one pH unit (down at gas on, up at gas off) doesn't effect the fish, which probably tells you all you need to know. 

CO2 ~ carbonate is a buffered system, which is why we have a stable pH value, and there are other pH buffers that will maintain pH at a specific level. I've never used the Waterlife pH buffers, but they are almost certainly based on <"phosphate buffers">, and probably NaH2PO4 and Na2HPO4.

The only thing these products do is separate you from your money. 





Fabio Perini said:


> How much truth is there in the statement that the PH of the water supply swings significantly? And if there is some truth in it, how do we protect our fish when using tap water?


You can just ignore pH, if you change some water fairly regularly you will always have hard water in the tank.





Fabio Perini said:


> is 17dKH referring to my area? I couldn't really find the figure in the water quality report from Affinity, I guess you need to calculate that from other parameters.


The 17dKH was for Corsham where I live, but it will be a similar value for all of the water that comes from a chalk or limestone aquifer, so most of the S. and E. of England. It is back to the equilibrium value for the CO2 ~ carbonate buffering system.  





Fabio Perini said:


> CALCIUM 115 mg/l Calcium is the principal constituent of hardness (dGH).
> TOTAL HARDNESS 287.5 mg/l..._The recognised classification scheme we are using is: 0-75 soft, 76-150 moderately hard, 151-300 hard, 300+ very hard. Your water is hard._
> Total hardness is usually expressed in terms of calcium carbonate and is measured in milligrammes per litre (mg/l) which is the same as parts per million (ppm). ....*Degrees German 16.1...*...


These are the values you need, your *dKH is 16.1*.

If you wan't the working for how you can work out how calcium, bicarbonate and hardness relate to one another they are in <"this post">. 

cheers Darrel


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## dw1305

Hi all, 





Fabio Perini said:


> I already have Chili Rasboras in an extremely soft water tank with zero KH, buffered by Shirakura Bee Sand.


I should have said that I keep soft water fish and that I use rain-water in my tanks, I occasionally cut it with some tap in the winter and some RO in the summer. 

I don't measure pH or hardness I just keep the tank water conductivity within a 80 - 150 microS range. 

The active substrate can soften the water via ion-exchange, there is a more complete discussion in <"Still very......">.

cheers Darrel


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## mort

Fabio Perini said:


> Hello Mort,
> 
> Thanks very much for the information which is quite comforting. How long have you been keeping the Panda and Adolfoi in the 24x12 tank? How many of them do you keep? Is it a Corys only tank? Out of curiosity, what do you do with the offspring?
> When you say you do partial water changes with RO, were you doing a 50/50 split or different? Was the tank setup initially as tap only or did you have RO in it from the start?
> I assume the tank to be planted?
> Sorry for the many questions, just very interested in your setup.
> Thanks in anticipation for the insight.
> Cheers,
> Fabio



Hi Fabio, 

The tank was setup with an RO tap mix of 70:30 because I was using it for breeding some wild apistogramma. I moved them on and just had 6 adolfoi in there. Since then I've been slowly changing the water by upping the tap percentage every water change (about 50% once a fortnight). I added the Panda cories a couple of months ago when I shut their tank down and have six beckfords pencilfish in there as well.
The plan is to eventually have a group of ten of one species, probably the adolfoi and create a similar tank for the others so I can get the breeding going. At the moment I have had 10 adolfoi cats survive without my intervention and gave some to a friend to breed and swapped some for some adults at a lfs to stop cross breeding.

The tank is a blackwater type setup with a little leaf litter, some buce and mosses tied to the twigs with emergent growth. This is really just a trial tank to see if I want to do the same thing on a larger scale. If I do I'll keep the two cory species and add more pencilfish above them.


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## Fabio Perini

dw1305 said:


> I'm cynical too, and <"I have a real problem"> with a lot of the sellers of aquarium products, they sell cheap chemicals, at an enormous mark-up, to rectify problems that don't really exist.



Darrel,
You're quickly becoming a hero of mine!  
You confirmed my suspicion that the guy was talking nonsense! And you've put my mind at rest as at first, I got really worried I was doing it all wrong...
Thanks ever so much!
All the very best,
Fabio




dw1305 said:


> I don't measure pH or hardness I just keep the tank water conductivity within a 80 - 150 microS range.



I assume you use a TDS meter to measure the conductivity? Are those fairly cheap TDS pens good enough? What would you recommend to have reliable readings? 

I'm trying to get away from active soils as I've realised they are time bombs as you never know when they will get totally depleted causing your tank to crash (in case of no KH)... Any pearls of wisdom on that? My tank has been running for two years now and from what I hear people tend to change the active soil for shrimp approx. once a year just to make sure. I don't have patience with that so I'm going to move to sand and mix tap and RO.
Cheers


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## Fabio Perini

mort said:


> The tank was setup with an RO tap mix of 70:30 because I was using it for breeding some wild apistogramma. I moved them on and just had 6 adolfoi in there. Since then I've been slowly changing the water by upping the tap percentage every water change (about 50% once a fortnight). I added the Panda cories a couple of months ago when I shut their tank down and have six beckfords pencilfish in there as well.
> The plan is to eventually have a group of ten of one species, probably the adolfoi and create a similar tank for the others so I can get the breeding going. At the moment I have had 10 adolfoi cats survive without my intervention and gave some to a friend to breed and swapped some for some adults at a lfs to stop cross breeding.



Hi Mort,

I assume your tap is already fairly soft? Or is it hard like mine? I do like Corydoras Duplicareus which is similar in size to the Panda, but, as Darrel mentioned that would require soft water as it comes for the upper Rio Negro.

How did you source your Panda and Adolfoi? 

Cheers,
Fabio


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## mort

Fabio Perini said:


> Hi Mort,
> 
> I assume your tap is already fairly soft? Or is it hard like mine? I do like Corydoras Duplicareus which is similar in size to the Panda, but, as Darrel mentioned that would require soft water as it comes for the upper Rio Negro.
> 
> How did you source your Panda and Adolfoi?
> 
> Cheers,
> Fabio



Our tap water is described as very hard by our water company. 

My panda were picked up from a lfs and are tank bred imports. The adolfoi are also tank bred and were a special order. I've had them a few years now but they seem available quite often.

If you can do RO then it's good but I often see people advise that tap is so much easier. I have RO because I make my own for my marine tank anyway so it's easy, the waste is collected to water my garden, but it is nice to be able to simply use tap if need be. This winter I'm building some rain water collection for the tropical tank so might probably will stop my transition to tap water (it's something I only decided yesterday as a winter project and would expand what I could keep in the future).


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## dw1305

Hi all, 





Fabio Perini said:


> You confirmed my suspicion that the guy was talking nonsense!


 The subject areas of "pH", "pH measurement" and "fishes sensitivity to pH change" are really contentious.  Part of the problem is that pH is both a <"log10 scale and a ratio">, which means that two similar pH readings may occur in very different water, or that two very different pH recordings can come from the same water at different times.  

I look at changes in pH in terms of changes in  water chemistry. As you move towards pure H2O (rather than the dilute solution of salts, with H2O as the solvent, that we usually call "water") pH becomes less and less meaningful as a measurement. In very soft water small changes in water chemistry cause large changes in pH, but in hard (carbonate buffered) water large changes in water chemistry are required to lower pH.   

Before aquascapers started adding CO2 to tanks everyone would have said that a fall of pH from alkaline (~pH7.8) to acid (below pH7) in an hour will kill all your fish, but this has proved to be untrue. Changes in pH, caused by addition of CO2, are changes in the the amount of TIC, you have more TIC, and a larger proportion of that TIC is carbonic acid (H2CO3), and the pH falls, nothing else has changed.

A measurement of pH is really only useful if you have some idea of the carbonate buffering (the dKH) of the water. 





Fabio Perini said:


> I assume you use a TDS meter to measure the conductivity? Are those fairly cheap TDS pens good enough? What would you recommend to have reliable readings?


Yes, a cheap conductivity meter will give you a fairly accurate reading,  you need a <"low range meter"> (0 - 1999 microS). 

It isn't going to apply in absolutely every situation, but usually a high conductivity value (600micro S - 800 micro S) for your tap water indicates that the water is "hard" and pretty fully saturated with Ca++ and HCO3- ions (has high dGH and dKH), even higher values usually indicate there are other non-carbonate salts present as well (from EI, salt ingress or agricultural fertilisers etc.).

cheers Darrel


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## Conort2

Fabio Perini said:


> Hi Mort,
> 
> I assume your tap is already fairly soft? Or is it hard like mine? I do like Corydoras Duplicareus which is similar in size to the Panda, but, as Darrel mentioned that would require soft water as it comes for the upper Rio Negro.
> 
> How did you source your Panda and Adolfoi?
> 
> Cheers,
> Fabio


Duplicareus are fine in hard water. I have a group and they're doing great. Granted they haven't spawned yet but by all accounts they spawn ok in hard water, it's adolfoi whose eggs struggle to develop without soft water. I think most cories do well in whatever water you give them provided there are not extremes. You just may have some issues raising the spawn of species like adolfoi.

Cheers


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## Fabio Perini

dw1305 said:


> Before aquascapers started adding CO2 to tanks everyone would have said that a fall of pH from alkaline (~pH7.8) to acid (below pH7) in an hour will kill all your fish, but this has proved to be untrue. Changes in pH, caused by addition of CO2, are changes in the the amount of TIC, you have more TIC, and a larger proportion of that TIC is carbonic acid (H2CO3), and the pH falls, nothing else has changed.



Hi Darrel,

Thanks very much for the exquisite explanation. I do understand it's a contentious matter, no doubt, like many things in life. However, when somebody tells you that they have to use buffers to avoid swings caused by the chemicals treatments from the water company, it truly seems far fetched because I had never heard this from other shops! Which is why I then decided to turn to you guys for guidance. Thanks again!

I know we are maybe getting slightly off topic, however I've been noticing a huge difference in the way that plants grow in my RO plus GH+ minerals and my other tank which is just tap water. Limnobium reproduces easily, plants are healthy and thriving in the RO tank... while in the tap water tank plants are struggling. I'm sure you probably already know where the issues might be, probably again water chemistry. Would the full water report from Affinity contain some clues regarding possible deficiencies or problems?

Once again your attention is much appreciated.

Cheers,
Fabio


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## Fabio Perini

mort said:


> If you can do RO then it's good but I often see people advise that tap is so much easier. I have RO because I make my own for my marine tank anyway so it's easy, the waste is collected to water my garden, but it is nice to be able to simply use tap if need be. This winter I'm building some rain water collection for the tropical tank so might probably will stop my transition to tap water (it's something I only decided yesterday as a winter project and would expand what I could keep in the future).



Hi Mort,

I'm doing RO already for a 30 liters shrimp tank. That is doable, but I wouldn't fancy doing that on a 90 liters tank, especially mixing tap and RO, would need loads of space where to mix the water and logistically would be an issue as I cannot produce my own RO and going to the LFS continuously to pick up RO would really spoil the fun of keeping fish.
Good luck with the rain collection! It looks like Darrel is very happy with his. I wouldn't do it where I live because of Heathrow and the vicinity with the Big Smoke which could be a source of undesirable contaminants.

Cheers,
Fabio


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## Fabio Perini

Conort2 said:


> Duplicareus are fine in hard water. I have a group and they're doing great.



Hello Conort2,

Nice to know! Thanks for sharing that. How long have you had yours for? What size tank do you use for them? I don't think I will want to breed them, however, if it did happen I would find it quite rewarding.

Cheers,
Fabio


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## Conort2

Fabio Perini said:


> Hello Conort2,
> 
> Nice to know! Thanks for sharing that. How long have you had yours for? What size tank do you use for them? I don't think I will want to breed them, however, if it did happen I would find it quite rewarding.
> 
> Cheers,
> Fabio


Only had this group for a couple of months now, they're with a group of gold lasers and quite a few other small community fish. To be honest the stock needs thinning out in there, there are too many different species it doesn't look very natural.

 They're in a tank that's 30inches long x 20inches wide x 16 inches high. They seem to be doing well, however I only have one definite female so am on the looo out for my wild caughts.

Cheers


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## Fabio Perini

Conort2 said:


> Only had this group for a couple of months now, they're with a group of gold lasers and quite a few other small community fish. To be honest the stock needs thinning out in there, there are too many different species it doesn't look very natural.
> 
> They're in a tank that's 30inches long x 20inches wide x 16 inches high. They seem to be doing well, however I only have one definite female so am on the looo out for my wild caughts.



We always seem to run into those issues. I'm sure you're right, tank however is nice and wide so I'm sure they're happy.

Good luck with finding some nice wild caught females!

Cheers,
Fabio


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## dw1305

Hi all,





Fabio Perini said:


> however I've been noticing a huge difference in the way that plants grow in my RO plus GH+ minerals and my other tank which is just tap water. Limnobium reproduces easily, plants are healthy and thriving in the RO tank... while in the tap water tank plants are struggling. I'm sure you probably already know where the issues might be, probably again water chemistry.


I actually use a floating plant (and usually _Limnobium_) as an indicator of nutrient deficiencies, this is mainly because you can discount CO2 shortage as a cause of any symptoms. I called it this method the <"Duckweed Index">, partially because it was an alternative approach to <"Estimative Index">, using Duckweed (_Lemna minor_), and also because they were both methods that didn't require the tank owner to carry out any water testing.

I originally used _Lemna minor_ because it was the plant used in <"water quality bio-assay">, but it is always yellow in soft water, even when there are high nutrient levels. _Limnobium_ has the advantage of growing over a large range of water hardness and nutrient levels, all that differs is the size and vigour of the plant.





Fabio Perini said:


> Would the full water report from Affinity contain some clues regarding possible deficiencies or problems?


It would, but you can already make some informed guesses based on geology.

Your water is hard and the limestone and chalk aquifers in the UK are fairly pure CaCO3, it hasn't undergone <"dolomotization and tends to have low magnesium levels">.  Adding magnesium (Mg) is always a good idea. "Epsom Salts" (10% Mg)  are an easily obtainable, and cheap, source.  Hard water and high levels of calcium effect the uptake of iron, you need to add chelated iron. Have a look at <"Duckweed Index says ....">.

Both magnesium and iron deficiencies cause yellow leaves (chlorosis), but if your new leaves are small and yellow? iron is the answer. Chlorosis in older leaves can be caused by more elements, the two most likely are nitrogen (N) and potassium (K), usually these are in reasonable amounts in SE England, but they may be deficient if your water comes from a very deep limestone aquifer. You can add them both via potassium nitrate (KNO3).  After carbon (C) plants need most nitrogen and potassium, which is why <"they can often limit plant growth">.

A final option is the third macro-nutrient phosphorus (P), but it is less likely to be in short supply. Magnesium and/or iron deficiency are the most likely options. 

Really healthy Amazon Frogbit looks like @Timon Vogelaar's in this thread <"Do we really need...">.

cheers Darrel


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## Oldguy

Fabio Perini said:


> slavery of RO for a bigger tank


If you want to reduce total hardness and you have the facility to catch and store rain water you can always pump this to your tank via an inline heater. Living in West Gloucestershire rain fall is pretty good and my wife lets me collect water butts, (I come back from the tip with more stuff than I take) but this is not possible for some people. I do wonder at the things people buy from their lfs. I think that the freshwater hobby read too much marine reef tank info especially about stability of water chemistry.


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## dw1305

Hi all,


Oldguy said:


> Living in West Gloucestershire rain fall is pretty good and my wife lets me collect water butts


Same for me, I don't live far away and <"I've always used rain-water">, right back into the 1970's.

I ran into to <"Nick Ridout"> recently, and he told me that I was the person that originally told him he could use rain-water in his tanks, although I have no recollection of this.

cheers Darrel


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## Oldguy

dw1305 said:


> I ran into to <"Nick Ridout"> recently,


Interesting thread. Always delighted with the flow of information on this forum. Also thought about Daphnia but have not got round to doing anything about it yet. I collect from the garage roof and keep leaf liter in the gutter (in reality can't keep it out, a silver birch overhangs the roof.) Can collect 40 gals in a day if Welsh rain comes in. Trying to pluck up courage to move a 100ltre slim line into the Conservatory. Will have to catch the wife in a good mood. Nice pics of your garden.


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## Fabio Perini

dw1305 said:


> Adding magnesium (Mg) is always a good idea. "Epsom Salts" (10% Mg) are an easily obtainable, and cheap, source. Hard water and high levels of calcium effect the uptake of iron, you need to add chelated iron. Have a look at <"



Hello Darrel,

Apologies for the long pause, I caught a bug that knocked me off the grid for some time..

I found fairly cheap Epsom Salts at Bridgewater Garden Supplies but it's 16% Mg... Could it still do or it's not for our purposes? Here they talk about 4 grams per litre in garden applications..would that be the same for aquaria?

Thanks very much,
Fabio


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## Fabio Perini

dw1305 said:


> Both magnesium and iron deficiencies cause yellow leaves (chlorosis), but if your new leaves are small and yellow? iron is the answer. Chlorosis in older leaves can be caused by more elements, the two most likely are nitrogen (N) and potassium (K), usually these are in reasonable amounts in SE England, but they may be deficient if your water comes from a very deep limestone aquifer. You can add them both via potassium nitrate (KNO3). After carbon (C) plants need most nitrogen and potassium, which is why <"they can often limit plant growth">.



Hi Darrel,

I guess a picture says a thousand words..I've got a mix of dwarf water lettuce, amazon frogbit and duckweek I believe, as this was not intentional but arrived together with the water lettuce...

If it is duckweed, it's definitely the most successful plant I'm growing! Just to give you an idea, the last picture shows how much I have to throw away every month to create some space for the other floaters to grow...

Although it's soft water, I don't see any yellowing of those tiny leaves, which is why I'm not sure whether it is duckweed.

The crypts funny enough have started showing holes in them and yellowing (more like whitening) of the leaves. I know the picture is poor but hopefully clear enough to show the problem. 

Thanks as usual for your input.

Cheers,
Fabio


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## Fabio Perini

dw1305 said:


> Hard water and high levels of calcium effect the uptake of iron, you need to add chelated iron. Have a look at <"Duckweed Index says ....">.



My hard water tank instead is where growth is really less than satisfactory. Even duckweed doesn't seem to multiply like in the other tank...

Any ideas?

Cheers,
Fabio


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## dw1305

Hi all, 





Fabio Perini said:


> Epsom Salts at Bridgewater Garden Supplies but it's 16% Mg..


It is fine, it won't be 16% magnesium when you use it, it will be 10% Mg, it is just because of the differing <"water of crystallization">. 





Fabio Perini said:


> Here they talk about 4 grams per litre in garden applications..would that be the same for aquaria?


No, but you can use the <"Rotala Butterfly Nutrient Calculator"> to give you an amount to add.

The maths is easy for "Epsom Salts",  because they are ~10% Mg.  If you have a 100 litre tank and add 5g of "Epsom Salts" gives you 5ppm Mg in the tank water. Five ppm would be fine as an amount to aim for.





Fabio Perini said:


> Although it's soft water, I don't see any yellowing of those tiny leaves, which is why I'm not sure whether it is duckweed.


Definitely Common Duckweed (_Lemna minor_). The leaves are actually a bit yellow, when it is really enjoying itself it is a dark green (like the three colours on the right of the Nitrogen LCC below).






Fabio Perini said:


> The crypts funny enough have started showing holes in them and yellowing (more like whitening) of the leaves.


That looks like the older leaves are senescing, it may be a light, rather than nutrient, effect. I thin out the floating plants in the winter, because there is a lot less ambient light. 





Fabio Perini said:


> My hard water tank instead is where growth is really less than satisfactory


The new leaves look good on the Frogbit (_Limnobium_), which makes me think that the older leaves were suffering from iron deficiency.

cheers Darrel


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## Fabio Perini

dw1305 said:


> It is fine, it won't be 16% magnesium when you use it, it will be 10% Mg, it is just because of the differing <"water of crystallization">.



That's great Darrel,
I'll get it ordered then.




dw1305 said:


> No, but you can use the <"Rotala Butterfly Nutrient Calculator"> to give you an amount to add.



Thanks very much for sharing this very useful tool. 




dw1305 said:


> Definitely Common Duckweed (_Lemna minor_). The leaves are actually a bit yellow, when it is really enjoying itself it is a dark green



That shows my knowledge on Lemna Minor! You mentioned before that this is really a soft water factor, which is why you switched to Limnobium Laevigatum for the Index. So there's really nothing I can do to improve its look, right?




dw1305 said:


> That looks like the older leaves are senescing, it may be a light, rather than nutrient, effect. I thin out the floating plants in the winter, because there is a lot less ambient light.



Point taken! I will definitely do that!




dw1305 said:


> The new leaves look good on the Frogbit (_Limnobium_), which makes me think that the older leaves were suffering from iron deficiency.



It looks like I should add some chelated iron to the tank... Any recommendations on where to get the right one? Is it dosed dry like the Epsom Salts or in a solution? Shall I use the Rotala Butterfly Nutrient Calculator for dosing it? I thought I had read something about iron and algae in one of your posts but I'm not sure. 
Much appreciated!

Cheers,
Fabio


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## dw1305

Hi all, 





Fabio Perini said:


> So there's really nothing I can do to improve its look, right?


You can pinch off the older leaves from both the _Pistia _and the _Limnobium, _once they've started to yellow and senesce they aren't helping the plant.  





Fabio Perini said:


> It looks like I should add some chelated iron to the tank... Any recommendations on where to get the right one? Is it dosed dry like the Epsom Salts or in a solution? Shall I use the Rotala Butterfly Nutrient Calculator for dosing it?


 You can dose it dry and use the Rotala Butterfly calculator. I use FeEDTA, but in harder water one of the <"other chelators is better">.





Fabio Perini said:


> I thought I had read something about iron and algae in one of your posts but I'm not sure.


It is in the <"_Rotala rotundifolia_ growth issue"> thread. 





Konrad Michalski said:


> After dosing some additional Iron (only about 2ml/day) my glass became green after 4 days. After 7 days I had to scrape it off as it looked disgusting. Now stopped dosing it again and my glass is clean again.





dw1305 said:


> I think that shows pretty conclusively that your plants are iron (Fe) deficient. All the green algae (those with the same photosynthetic pigments as the mosses, ferns and higher plants) have the same photosynthetic systems and pathways.





Konrad Michalski said:


> Darrel, I don't quite understand why?





dw1305 said:


> The algae was iron limited (in terms of Liebig's law of the minimum), but could show a rapid greening due to the diffusion of Fe ions into every cell. Once you stopped adding the higher dose of iron, Fe ions went out of solution and it became the limiting nutrient again. Your plants will have taken up iron ions during the period when iron was available, *but they won't show a rapid response in greening because they can't move iron ions to the yellow, chlorotic leaves, it is only new leaves that will be greener.*


 One of the advantages of Duckweed (_Lemna minor_) is that it has relatively few cells and a <"very quick generation time">, which makes it more like a green algae in its response. 

cheers Darrel


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## Fabio Perini

dw1305 said:


> You can pinch off the older leaves from both the _Pistia _and the _Limnobium, _once they've started to yellow and senesce they aren't helping the plant.



Hi Darrel, 
Sure, I do this regularly, just behind with the maintenance due to the bug and also cause I wanted to show you the state of the plants. Much appreciated.




dw1305 said:


> It is in the <"_Rotala rotundifolia_ growth issue"> thread.



That's absolutely great! I wouldn't have probably managed to find it again!




dw1305 said:


> One of the advantages of Duckweed (_Lemna minor_) is that it has relatively few cells and a <"very quick generation time">, which makes it more like a green algae in its response.



So if I understand correctly the point you're making would this be a twofold kind of advantage? Will the Lemna compete with the algae for the iron or will only darken quicker than other plants?
Thanks very much!
Cheers,
Fabio


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## dw1305

Hi all,





Fabio Perini said:


> Will the Lemna compete with the algae for the iron or will only darken quicker than other plants?


Both really, it has a fast potential growth rate, it is in bright light and it isn't CO2 limited, all of which means that it will take in nutrients at a fast rate. The distinction between the green algae and plants is really just an arbitrary one, it is better to think of them all <"as plants">, plants are  - "the plants you want" and algae - "the plants you don't want".  

_Lemna_ will show a quick response to the <"non plant mobile nutrients">, because it has a really quick generation time for producing new leaves, algae will show an even quicker response, because all their cells are in contact with the water, they don't have any internal "plumbing". For the mobile elements it doesn't make much difference, because all plants can move the elements to both new and old leaves. This is why you get a really quick greening response when you add nitrogen (N), potassium (K), magnesium (Mg) etc. and it was the element that was <"limiting plant growth">.

cheers Darrel


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## Fabio Perini

Hi Darrel,

That is, as usual, a great response and I keep learning a lot from all those links you always kindly provide! Thanks very much!
Cheers,
Fabio


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## Fabio Perini

dw1305 said:


> Both really, it has a fast potential growth rate, it is in bright light and it isn't CO2 limited, all of which means that it will take in nutrients at a fast rate. The distinction between the green algae and plants is really just an arbitrary one, it is better to think of them all <"as plants">, plants are - "the plants you want" and algae - "the plants you don't want".



Great distinction Darrel, totally agree.

One last question regarding the Epsom Salts. Can I dose it dry straight into the tank which has got snails, shrimp and one Betta Splendens? Or is it better to dilute it in water first?

Cheers,
Fabio


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## dw1305

Hi all,





Fabio Perini said:


> Can I dose it dry straight into the tank which has got snails, shrimp and one Betta Splendens? Or is it better to dilute it in water first?


It has really high solubility, so even if you dose it dry it will almost instantly dissolve.

cheers Darrel


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## Fabio Perini

dw1305 said:


> It has really high solubility, so even if you dose it dry it will almost instantly dissolve.



Much appreciated Darrel.

Wish you and your family a very Merry Christmas and a wonderful New Year!

All the very best,
Fabio


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