# Tap water or Rain water??



## maj74 (15 Oct 2020)

I ran a Discus tank several years ago, and used only rain water very successfully.

My return to aquascaping won't be discus, but an 80cm high tech planted tank.

I will bring a water feed in from outside to a sump under the tank, so that water can come up to room temp before carrying out water changes.

I can't decide whether to bring in tap water or rainwater? I know rainwater has the advantages of no chlorine etc for livestock, but also know it's lack of hardness can cause issues with CO2 injection and PH crashes.

What are peoples' thoughts on which I should use? do the benefits of one outweigh the negatives?


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## Tim Harrison (15 Oct 2020)

maj74 said:


> it's lack of hardness can cause issues with CO2 injection and PH crashes.


Can it, is that from personal experience or info from another source?


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## dw1305 (15 Oct 2020)

Hi all,
I've been a rain-water user since the 1970's and I would always prefer it to tap water. I'm <"pretty risk adverse">, and I honestly think <"it is a safer option">.





maj74 said:


> I know rainwater has the advantages of no chlorine etc for livestock, but also know it's lack of hardness can cause issues with CO2 injection and PH crashes.


You can re-mineralise rain-water like you would RO water.  Rain water tends to be <"more variable during the year">, so rather than adding a set amount of dGH/dKH I use a <"conductivity meter to give me a datum range"> where plant growth is acceptable. I don't add a specific mix to raise hardness, we have a hard tap supply (about 18dKh/dGH and ~all from Ca++ and 2HCO3- ions), so I just mix in some tap if the values falls below about 80 microS (50 ppm TDS).

I'm not a CO2 user, but most of what you read about <"pH crashes and  pH stability is wrong">, there is a more complete explanation in the linked thread, <"Is there a need to......">. <"Chemical buffering is quite a complex area">, and my personal opinion is that some unscrupulous companies have exploited this to <"sell worthless products">. 

When you add CO2 you change the <"equilibrium point of the carbonate ~ CO2  buffered system, and the pH falls">.

cheers Darrel


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## Conort2 (15 Oct 2020)

I have started using rainwater following @dw1305 recommendation as I now keep soft water species that need low tds water. I can’t say I’ve had any issues and I am still using co2. Plant growth is better than it was I believe my hard water affected nutrient uptake. I have also switched to a lean dosing method following the change as I don’t think my species would appreciate the high tds associated with ei dosing and the plants are still growing great.

I have no idea what my ph is and Do not worry about it, my fish are from soft water/ black water areas so I know they can deal with a really low ph. I rely on my tds to tell me if my water I suitable for my fish and try and keep it under 100ppm. Think my rainwater has a tds of around 40/50 but time ferts and what no are added it goes up some what.

cheers

Conor


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## Oldguy (15 Oct 2020)

maj74 said:


> I cant decide whether to bring in tap water or rainwater?


Why not mix the two together to get the hardness you want. I go for a very soft mix and then increase hardness with magnum sulphate (Mg is a macro nutrient and is often lacking in UK tap water) 

Some tap waters have a high pH which is not related to hardness but is a result of water treatment. This can put a demand on injected CO2.

Very hard water can interfere with chelated trace & micro nutrients by GpII competition, but this can be overcome by using a more stable chelating agent. There are lots of threads on this subject in this forum.

Measurement of both pH and Total Dissolved Solids (TDS) is problematic with very soft waters.

Chemicals in solution are there as independent ions and are not there as the compounds that were put in ie MgSO4 and KNO3 are there as Mg++ ions K+ ions
 SO4- - ions and NO3- ions. Think of it as a super swingers party.

Most plants appear not to be hardness sensitive with a few that are.

With the Estimated Index (EI) approach are nutrients are in excess it is a matter of balancing light and carbon dioxide (often a circulation issue). For many the lights are too bright and on for too long. 

Start with lots of fast growing plants and thin out and replace once the tank as settled down.

Allelopathy between higher plants and algae is an issue that needs exploring. Good planted tanks have no algae issues, those with poor plant growth have algae issues. Allelopathy may be contentious but is worth considering.


Good luck with your endeavors.


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## hypnogogia (15 Oct 2020)

Yup, second rain water cut with tap to get the first hardness.  Where I am I also need to be careful of phosphate sin the top water, so the amount off tap I add depends on the time of year.  We have lower phosphates in winter.


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## maj74 (15 Oct 2020)

Tim Harrison said:


> Can it, is that from personal experience or info from another source?



Not from personal experience - never had a problem with my Discus tank, but then it wasn't heavily planted with lots of CO2

I may have remembered incorrectly, but I thought a lack of hardness meant low buffering capacity and risk of pH changes.



Oldguy said:


> Why not mix the two together to get the hardness you want. I go for a very soft mix and then increase hardness with magnum sulphate (Mg is a macro nutrient and is often lacking in UK tap water)
> 
> Some tap waters have a high pH which is not related to hardness but is a result of water treatment. This can put a demand on injected CO2.
> 
> ...




I would prefer from a simplicity point of view, to use one or the other. I don't want to be bringing more hose feeds in from outside than I need to. I can connect the pipe into the house to either a water butt or the tap. Yes it would be technically feasible to switch between the two - but I am trying to keep the system as simple and hassle free as possible.



Oldguy said:


> Why not mix the two together to get the hardness you want. I go for a very soft mix and then increase hardness with magnum sulphate (Mg is a macro nutrient and is often lacking in UK tap water)
> 
> Some tap waters have a high pH which is not related to hardness but is a result of water treatment. This can put a demand on injected CO2.
> 
> ...



Here in Suffolk we have typically very hard water.


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## dw1305 (15 Oct 2020)

Hi all, 





maj74 said:


> I may have remembered incorrectly, but I thought a lack of hardness meant low buffering capacity and risk of pH changes


It does, but pH is never stable in soft water and that it isn't a problem for fish etc unless you keep Lake Tanganyika Cichlids etc. 





maj74 said:


> Here in Suffolk we have typically very hard water.


I would go with rain-water. You won't need very much tap water to give you some dGH/dKH, it is going to be a couple of litres at most, so <"wouldn't need plumbing in">. An issue might be <"lack of rain">?

@MirandaB is in <"your part of the world"> and she uses tap water and may be able to advise you on plants etc. if you wish to go down that route.

cheers Darrel


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## Conort2 (15 Oct 2020)

maj74 said:


> I would prefer from a simplicity point of view, to use one or the other. I don't want to be bringing more hose feeds in from outside than I need to. I can connect the pipe into the house to either a water butt or the tap. Yes it would be technically feasible to switch between the two - but I am trying to keep the system as simple and hassle free as possible.


Just go for rainwater then, I don’t bother cutting mine with anything. In the summer it’s a case of pumping directly from the water butt outside into the aquarium however now the temperature has dropped it’s pumped into a bin indoors first and preheated.

will you be going for domestic discus or wilds?

 Cheers

Conor


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## dw1305 (15 Oct 2020)

Hi all, 





Conort2 said:


> will you be going for domestic discus or wilds?





maj74 said:


> I ran a Discus tank several years ago, and used only rain water very successfully.  My return to aquascaping won't be discus, but an 80cm high tech planted tank.


I think the OP used to keep Discus in rain-water, but is now going to have a planted tank with other fish. 

cheers Darrel


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## maj74 (15 Oct 2020)

Conort2 said:


> Just go for rainwater then, I don’t bother cutting mine with anything. In the summer it’s a case of pumping directly from the water butt outside into the aquarium however now the temperature has dropped it’s pumped into a bin indoors first and preheated.
> 
> will you be going for domestic discus or wilds?
> 
> ...



It's not even discus. Just a high tech planted tank with Tetras of some sort. Its only 140-150 litres in total. I'm just putting lots of time and design into a piped / pumped setup, allowing semi automatic water changes, to keep maintenance time demands to a minimum.


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## Tim Harrison (15 Oct 2020)

I'd use rainwater too, but depending on how much storage capacity you have you might find yourself having to switch to tap or RO water during dry spells.


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## maj74 (15 Oct 2020)

Tim Harrison said:


> I'd use rainwater too, but depending on how much storage capacity you have you might find yourself having to switch to tap or RO water during dry spells.



That is a good point. We can be as dry as the UK gets over here....

However - The water butt and outside tap are next to each other - so switching the feed hose (to the storage sump under the tank) over wouldn't be a huge issue on the occasions in summer it proved necessary. Want to get away from having 25L water carriers sitting in the living room. - WAF and all that.


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## Conort2 (15 Oct 2020)

maj74 said:


> It's not even discus. Just a high tech planted tank with Tetras of some sort. Its only 140-150 litres in total. I'm just putting lots of time and design into a piped / pumped setup, allowing semi automatic water changes, to keep maintenance time demands to a minimum.


Apologies You did say in your initial post.

you’ll only be using roughly 70l a week so a couple of water butts linked together should last you a while. If you’re cutting with tap it should last even longer. You mention pumping directly from the butt, will you be be preheating the water somehow before?


cheers


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## MirandaB (15 Oct 2020)

dw1305 said:


> Hi all, It does, but pH is never stable in soft water and that it isn't a problem for fish etc unless you keep Lake Tanganyika Cichlids etc. I would go with rain-water. You won't need very much tap water to give you some dGH/dKH, it is going to be a couple of litres at most, so <"wouldn't need plumbing in">. An issue might be <"lack of rain">?
> 
> @MirandaB is in <"your part of the world"> and she uses tap water and may be able to advise you on plants etc. if you wish to go down that route.
> 
> cheers Darrel


 Yes I'm on the border but for most of my fish I've had to go RO/Tap mix now when there isn't enough rainwater to do a mix.
I used to use straight tap and it certainly wasn't an issue to growing plants although if using injected co2 it does mean you tend to use more co2 and of course the inevitable limescale build up is a pain.


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## maj74 (15 Oct 2020)

Conort2 said:


> Apologies You did say in your initial post.
> 
> you’ll only be using roughly 70l a week so a couple of water butts linked together should last you a while. If you’re cutting with tap it should last even longer. You mention pumping directly from the butt, will you be be preheating the water somehow before?
> 
> ...



It’s pumped into a sump in the cabinet so it can come up to room temperature.


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## rubadudbdub (16 Oct 2020)

Tim Harrison said:


> I'd use rainwater too, but depending on how much storage capacity you have you might find yourself having to switch to tap or RO water during dry spells.



I've not used them myself as I have started mixing rain water with tap, but Spotless water could be an easy RO back up without forking our for an RO unit you won't use for long periods.   The website says Bury St Edmunds or Ipswich when I type Suffolk into the location search.  

https://www.spotlesswater.co.uk/Loc...DRk_-eQOSI4qlWSstH8A4gHvpovA2nYxoCLA8QAvD_BwE


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## tam (16 Oct 2020)

Timely question, I'm just thinking of swapping from RO+remineraliser to rain+very hard tap. Checked the new water butt and it has a TDS of 25. Might need to flush it through a bit though as it is an ex whisky barrel  ... and it needs a tap adding.

We used to use rain when I was a kid and had great plant growth, but that was all low tech stuff.


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## dw1305 (17 Oct 2020)

Hi all,





tam said:


> Checked the new water butt and it has a TDS of 25. Might need to flush it through a bit though as it is an ex whisky barrel  ... and it needs a tap adding.


I think that should be fine.

It doesn't have many salts (ions) present because of the low TDS. If alcohol was still seeping out of the  wood, it wouldn't show as TDS (it isn't an ion), but it would be less dense than water, so it would form a surface layer, which would continually evaporate.

cheers Darrel


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## hypnogogia (17 Oct 2020)

tam said:


> as it is an ex whisky barrel


Happy fish!


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## Paulus (22 Feb 2021)

Here also thinking to get a rain barrel in the garden (after the other one broke/cracked because of the sun etc  few years ago ) or get a RO system......
But still not sure what to do or if it will collect enough rain to do the weekly water changes etc.
RO is always so slow and lots of waste water.


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## Andy Pierce (22 Feb 2021)

I guess the rainwater users are OK with the runoff from whichever surface the rainwater is collected. Do you do anything at all to purify/disinfect the rainwater or just use as is?


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## Oldguy (22 Feb 2021)

Paulus said:


> if it will collect enough rain to do the weekly water changes etc.





Andy Pierce said:


> rainwater users are OK with the runoff


Most weathered roofs are fine. A bit of bird poo is of no concern. Keep an eye out for slugs ( had an issue once, solved with a self adhesive cooper foil band around water butt and a circle of anti fouling paint.

I mix approx 50:50 rainwater to tap water (tap water moderately soft) never ran out of rain water in the west of the UK. (have three barrels in reserve but only ever used one of them)

Hope this is of some help. (never had pH crashes & I don't add buffers)


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## Paulus (22 Feb 2021)

Ordered a barrel today (was on sale  ) and will put it on a different location as before. This time in the shadow part of the garden.
Plan is to use a old pond pump which i now use inside a bucket in the sink to refill the tank.
But in the barrel i can put some fine filtering on the pump so it will collect large slug/muck etc.

Now i only need to wait for the order and rain.....


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## dw1305 (22 Feb 2021)

Hi all,


Andy Pierce said:


> Do you do anything at all to purify/disinfect the rainwater or just use as is?


I keep some <"_Daphnia_ in my barrels">. This won't work if you live somewhere where you get very pure rainwater, mine always has some carbonate hardness.

Have a search for <"Daphnia Bioassay">.

cheers Darrel


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## Paulus (26 Feb 2021)

Rain barrel is standing. Short rain period yesterday and the complete barrel is filled with 227 Liters 
Now getting some diy ideas to give it a simpel and replaceable prefilter option with some sponges or white filter floss etc.
Or maybe a 3d print like this Water filter for rain barrel by glsf91 

Nice things to do for the weekend


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## Paulus (28 Feb 2021)

Used the rainwater for the first time today with a water change.
Only used 60 liters (see this post for more info Rainwater confussion )

What i noticed was that the rainwater has a little bit of a white haze in it when filling the tank/jerrycans. It wouldn't of course not be as clear as tap water. But something to do about this? Over some time/hours the filter will take it out i think, but it doesn't look that fresh when viewing the tank


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## Simon Davey (1 Mar 2021)

Paulus said:


> Used the rainwater for the first time today with a water change.
> Only used 60 liters (see this post for more info Rainwater confussion )
> 
> What i noticed was that the rainwater has a little bit of a white haze in it when filling the tank/jerrycans. It wouldn't of course not be as clear as tap water. But something to do about this? Over some time/hours the filter will take it out i think, but it doesn't look that fresh when viewing the tank


Bacterial bloom in your new rainwater butt?


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## Paulus (1 Mar 2021)

Simon Davey said:


> Bacterial bloom in your new rainwater butt?


Could be. At least the only thing I can come up with 
Yesterday added some extra filter floss on the intake (it was sunny outside so nice to be in the garden instead of inside  )
Also flushed the barrel to get the bottom clean (some leftovers of the roof that came of during the heavy snow and was laying in the gutter.
Still need to add a leaf guard at the top of the rain pipe. But covid/closed stores......... They cost 1 euro but minimal cost to get a collect/pickup option is 25 euro -_- (and i only need 1  )


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## Paulus (11 Mar 2021)

The filter socks are working (bought a 6pack of them with 100micron)


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