# What TDS should I aim for?



## Sacha (10 Jan 2014)

I use RO water, and I remineralise using JBL Aquadur. 

I typically remineralise to a KH of 4. After dosing with EI, TDS ends up in the 300s. 

Should my TDS be lower? If so, that would mean using less Aquadur, which has two drawbacks. Lower KH means pH swings are more likely, and more acidic water means my Nerite snails will not be happy. 

So, what is the lowest "safe" KH for a Co2 enriched tank, and how do I make sure my Nerites stay happy in soft water...


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## kirk (11 Jan 2014)

I use ro and salty shrimp to 're mineralize.I've stopped ei as its the only way I can keep the tds right for our crs. Also turned co2 off and added an air stone. im now loosing plants and I'm considering a small nano for the crs as I'm not enjoying watching all my hard work floating around on the surface.   our tds is at 170 today .


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## Sacha (11 Jan 2014)

Hmm ok. Any idea what your KH is?


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## Ian Holdich (11 Jan 2014)

I used neat ro, and then used tropica ferts, they did a great job of re mineralising. If you're using EI, then in essence you're remineralising twice.


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## Sacha (11 Jan 2014)

Not true...

The fish need Calcium, Magnesium etc for their Osmoregulatory systems to function properly. Calcium especially- this isn't included in EI ferts. 

It's very important to remineralise RO water... Ferts alone do not provide the minerals which are vital to the fishes' health. 

Some South American species like Discus and Angelfish can get away with being in neat RO, but other species will suffer. 

Also without any carbonate in the tank, KH will be zero, which leads to a very unstable environment. 

Don't you get mad pH swings, because your KH will be non existent?


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## Andy Thurston (11 Jan 2014)

Just stop dosing magnesium in your ei mix it will probably be in the aquadur whats your Gh after you remineralise


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## Ian Holdich (11 Jan 2014)

Ok lol! 

Your calcium and mg is in your trace elements. 

Have a look at viktor Lantos's scapes, he does the same. Quite a lot of us do...


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## Sacha (11 Jan 2014)

Ok my mistake. but my main concern is how can you keep a tank stable without any Carbonate? With a KH of zero?


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## Sacha (11 Jan 2014)

Also, have any of you kept Nerite snails happy in acidic water for a decent period of time...


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## Ian Holdich (11 Jan 2014)

My kh was a steady 5-6

My tds was around 100

I was keeping quite sensitive chocolate gouramis at the time.


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## Sacha (11 Jan 2014)

How did you get a KH of 5-6 if you weren't remineralising? 

Were you adding carbonate somehow?


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## Ian Holdich (11 Jan 2014)

Presumably the calcium carbonate in the ferts and also the rocks in the tank. Seryu stone adds to tds.  I did dose the ferts quite heavily in the tanks I used with pure ro. 

Have a look through Amanos stuff, he also uses pure ro in his tanks. In his book 'the complete works', it gives you a lowdown on what the stats were in his tanks, and his kh was almost always 3-4. This is with real lean dosing.


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## Sacha (11 Jan 2014)

OK, thanks a lot for your advice.

Really I want my water to be as soft as it can reasonably be.

My concerns are really the health of the nerite snails, because I know they suffer from calcium deficiency in acidic water, and the risk of pH swings. I will have to get hold of that book I think.


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## Ian Holdich (11 Jan 2014)

I didn't have any snails in the tank, so can't comment on that. I'm sure it would have a slight impact on their shells though. I had shrimp in the tank and they were fine.


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## dw1305 (11 Jan 2014)

Hi all,





Sacha said:


> Ok my mistake. but my main concern is how can you keep a tank stable without any Carbonate? With a KH of zero?


 You can ignore pH in very soft water, pH is the ratio of acids and bases, and tells us nothing about amounts. Because you have very few bases (H+ ion acceptors), any small addition of acids (H+ ion donors) will lower the pH. All you have to remember is that large changes in pH reflect small changes in water chemistry.  





Sacha said:


> Also, have any of you kept Nerite snails happy in acidic water for a decent period of time...


 You can't, this is where both pH and carbonate buffering are important. Because the snail shell is calcium carbonate (in its aragonite form) it is a potential H+ ion acceptor, and if you place a shell into water with lots of H+ ions, they will rapidly erode the shell and kill the Nerite. A few snails are very efficient at extracting both calcium and carbonate from base poor environments, like Malaysian Trumpet Snails, and this allows them to grow in water that is slightly acid and calcium poor, but even in this ase the older whorls of the shell show erosion, and the MTS never grow very large. Red Ramshorn snails can also survive in water that is fairly calcium poor but neutral, as long as the pH doesn't spend too much time below pH7. 

I have some tanks (all rain-water but with some carbonate buffering from dust etc) where I can't keep Red Ramshorn or Tadpole snails because the water is just too soft, and one where even added MTS soon dissolve. In all the tanks all the older snail shells are white, and very thin, and I don't have any large old snails. I can't keep any other snails for long, even ones like Assassin snails, which people have successfully kept in soft water set-ups.

cheers Darrel


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## Sacha (11 Jan 2014)

Wow thanks a lot for that response Darrel.

I have nerite snails who have been living in this tank for years now. For at least one year, the pH has been below 7, and the KH below 4.

Are you telling me these snails are suffering in any way? Their shells appear "healthy", although they have changed colour since I got them, from a dark brown, to a light orange colour. 

Is there any way I can keep the snails healthy in a Co2- enriched tank?


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## dw1305 (11 Jan 2014)

Hi all,





Sacha said:


> Are you telling me these snails are suffering in any way? Their shells appear "healthy", although they have changed colour since I got them, from a dark brown, to a light orange colour.


I'd imagine they are probably all right. The fact that the shell has changed colour maybe because the outer layer are being eroded, if this is the case I'd expect the older whorls to be lightest and the newer shell material around the mouth of the shell to be darkest. If they haven't grown? it maybe that they can't make new shell. 





Sacha said:


> Is there any way I can keep the snails healthy in a Co2- enriched tank?


 I don't know the answer to this one, but some-one who has a high tech. tank and snails should be able to. When you depress the pH using CO2, you are altering the CO2 ~ HCO3- equilibrium, which gives you the strange situation of having low pH in (potentially) carbonate rich water. 

cheers Darrel


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## Ian Holdich (11 Jan 2014)

Actually, I did once have a nerite in ro water, this was c02 enriched. You can see the c02 whiz zing past it. 




 

He looks ok. He did last as well, until he made an escape from an open top tank.


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## kirk (11 Jan 2014)

That's what I've heard if they don't like it they make for the lounge floor Or walls


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## Sacha (11 Jan 2014)

Mine does spend most of his time above the water line


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## Ady34 (11 Jan 2014)

I have 2 of these little horned nerites.
My TDS is currently 167 and never goes higher than 220. My tap water has a kh of around 2 and a gh of around 2 also. I use tap water for water changes but do have a lot of seiryu stone which may add to the mineral content slightly (don't know tank kh as don't test) but wouldn't guess too much as TDS is low. I inject co2 which depresses ph to the low 6's during the photoperiod, but rises to above ph7 after the photoperiod.
Whilst both snails are active and seemingly ok, they havnt grown much or developed horns which I'm guessing is down to the struggle of obtaining the necessary elements for shell development. Ramshorns do ok and reproduce, but don't have a nice sheen to their shells.
Nerites can survive in high tech soft water tanks, but don't thrive IMO. 
Cheerio,
Ady.


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## REDSTEVEO (29 Apr 2015)

Sacha said:


> Also, have any of you kept Nerite snails happy in acidic water for a decent period of time...


I tried keeping nerite snails in my discus tank - epic fail I am afraid, none of them survived, the acid water destroys the shells


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## sciencefiction (30 Apr 2015)

Well, I myself still have a problem with snail shell erosion in one single tank. It started maybe more than a year ago. I have hard water, no issues at all in other tanks. In this tank all the Malaysian trumpets and pond snails have died in the last year.  There are 5-6 small surviving ramshorn snails a few of them with eroded shells. I can't figure it out. Gh 12, Kh 8, ph 7.4, TDS around 300-ish, weekly large water changes, no dewormers ever added, bought the tank new.
The interesting part is the plants are doing a lot better since that started happening and the substrate is very old plain sand, full of mulm. My guess is it's gone quite acidic for trumpet snails maybe...but the ponds snails are gone too....
Maybe that substrate is acting like a magnet for stuff the snails need....I have no idea actually...


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## roadmaster (1 May 2015)

Sacha said:


> Not true...
> 
> The fish need Calcium, Magnesium etc for their Osmoregulatory systems to function properly. Calcium especially- this isn't included in EI ferts.
> 
> ...




Believe many who use R/O do so because they have fairly hard, to rock hard water and are maybe trying to keep soft water species and possibly breed same..
Many of these folks, use their tap water to provide remineralization 60/40 50/50 R/O tap water, for it likely has enough calcium/magnesium for fish plant's.
Fish food's also contain calcium and often enough to provide for the fishes development.


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## sciencefiction (1 May 2015)

Soft water species are capable of utilizing low calcium/magnesium availability in the water. However, being the sceptic I am, one needs to know whether those people's fish lived their full life spans in whatever conditions they were kept in. Very soft water in a fish tank is not as stable as  the one fish encounter in the wild. I'd probably only do it for breeding purposes then go back to more stable stats long term in the range the fish can tolerate.


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## dw1305 (1 May 2015)

Hi all,





sciencefiction said:


> Soft water species are capable of utilizing low calcium/magnesium availability in the water. However, being the sceptic I am, one needs to know whether those people's fish lived their full life spans in whatever conditions they were kept in. Very soft water in a fish tank is not as stable as the one fish encounter in the wild.


 Depends on the fish, but black-water fish really are different *and need* to be maintained in very soft, acidic water containing humic compounds. 

If you have a look on the  <"_Parosphromenus_ Project"> or <_Apistogramma_ Forum"> you can get an idea of the water parameters.

One problem is that these fish come from waters where there are very low bacterial loads, and are very prone to infection in water with higher microbial loads. The relative lack of bacteria is because of the very low nutrient levels, presence of anti-microbial tannic & humic compounds and the acidity of the water.  

If they were easy to keep fish like _Satanoperca_ spp., Heckel Discus, Altum Angels, _Apistogramma diplotaenia_ etc. would be much more available.

Have a look at <"Chemical characterization of the rivers in the Rio Negro basin">.

cheers Darrel


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## sciencefiction (1 May 2015)

dw1305 said:


> Depends on the fish, but black-water fish really are different and need to be maintained in very soft, acidic water containing humic compounds



Yes Darrel. However, they still need Ca and Mg even in those soft/acidic conditions. There's no fish alive that doesn't. I presume this is one of the reasons why its hard keeping them in a fish tank.


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## Andy Thurston (1 May 2015)

sciencefiction said:


> Yes Darrel. However, they still need Ca and Mg even in those soft/acidic conditions. There's no fish alive that doesn't. I presume this is one of the reasons why its hard keeping them in a fish tank.


I thought they got Ca and Mg from their diet instead


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## sciencefiction (1 May 2015)

Big clown said:


> I thought they got Ca and Mg from their diet instead



I presume they can but it will have an impact on retention of other life sustaining minerals instead. So supplementing via food only I think is not going to be ideal and will have an impact on growth/development and health.


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## Andy Thurston (1 May 2015)

not really because they come from waters where these minerals are in short supply, maybe keeping hard water species in soft water would be a big problem and vice versa. I would think the waste products in their water would harm them before they had a Mg or Ca shortage, if they were fed correctly


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## sciencefiction (1 May 2015)

This study is interesting below about C.adolfoi exposed to Ca2+ free water.

_The present study analyzes Na+ and K+ disturbances caused by low pH in two catfish species from the Amazon River. Corydoras adolfoi inhabits ion-poor, black-stained, low pH (3.5-4.0) waters, while C. schwartzi is native to ion-rich waters at circumneutral pH. Fish were exposed to pH 3.5 Ca2+-free, and Ca2+-enriched (approximately 500 micromol/l) water to determine the protective effects of calcium. Net Na+ and K+ fluxes were measured in the water collected from the fish experimental chambers. C. adolfoi was unable to control the Na+ efflux at low pH, exhibiting Na+ loss up to -594 +/- 84 nmol g(-1) h(-1) during the first hour. After 3 and 6 h, net Na+ flux increased by 7- and 23-fold, respectively. In C. schwartzi, at pH 3.5, the initial high Na+ loss (-1,063 +/- 73 nmol g(-1) h(-1)) was gradually attenuated. A K+ loss occurred in both species, but remained relatively constant throughout exposure. High [Ca2+] affected ion losses in both species. C. adolfoi had 70% loss attenuation, indicating incapacity to control Na+ efflux. In C. schwartzi, elevated [Ca2+] completely prevented the Na+ losses caused by exposure to low pH. Rather different patterns were seen for K+ fluxes, with C. adolfoi showing no K+ disruption when exposed to low pH/high [Ca2+]. Thus, C. adolfoi loses Na+ during acid exposure, but has the ability to control K+ loss, while C. schwartzi controls diffusive Na+ loss but exhibits a slightly higher K+ loss. Ion balance was influenced by [Ca2+] at low pH in C. schwartzi but not in C. adolfoi._


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## sciencefiction (1 May 2015)

sciencefiction said:


> Well, I myself still have a problem with snail shell erosion in one single tank. It started maybe more than a year ago. I have hard water, no issues at all in other tanks. In this tank all the Malaysian trumpets and pond snails have died in the last year.  There are 5-6 small surviving ramshorn snails a few of them with eroded shells. I can't figure it out. Gh 12, Kh 8, ph 7.4, TDS around 300-ish, weekly large water changes, no dewormers ever added, bought the tank new.
> The interesting part is the plants are doing a lot better since that started happening and the substrate is very old plain sand, full of mulm. My guess is it's gone quite acidic for trumpet snails maybe...but the ponds snails are gone too....
> Maybe that substrate is acting like a magnet for stuff the snails need....I have no idea actually...



Took a picture of a snail just now. All info points my snails shouldn't have calcium deficiencies in my hard water. The rest of the survivors are about the same size, some have normal appearing red shell, some white. Anyone venturing a guess why this is happening in a hard water tank? Water is changed at 50% weekly for around a year without a fail. The issue is just in the one tank with the same tap water as in the rest 4 tanks I have.








.


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## sciencefiction (1 May 2015)

Sacha said:


> I use RO water, and I remineralise using JBL Aquadur.
> 
> I typically remineralise to a KH of 4. After dosing with EI, TDS ends up in the 300s.
> 
> ...



Sorry for intruding with my snail issue Sacha. I just thought it maybe useful if someone has an idea as it seems it's not all about Kh, TDS, ph, etc..

My guess about the above questions is that Kh value in a CO2 tank won't matter as the CO2 has very little impact on Kh. It only moves the Ph.
As for reconstituting the water, it all depends on what you use to increase the TDS. I'd just use the same remineralisation product and aim at the same TDS for new water without worrying about Kh, Gh and Ph much. Just go by what your snails are telling you 
Mine did well in TDS of 200, Gh around 6-7 and Kh of 2, stable ph of 7.4 in a low tech non-co2 tank.
The Kh value you need in order to keep the Ph stable would be unique to your own tank setup, type of water used for water changes, amount of bioload added, etc..maybe some trial and error is needed. I don't think there's one formula for all.


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## dw1305 (1 May 2015)

Hi all,





sciencefiction said:


> Yes Darrel. However, they still need Ca and Mg even in those soft/acidic conditions. There's no fish alive that doesn't. I presume this is one of the reasons why its hard keeping them in a fish tank.


No, I'm not arguing that they don't need salts like Ca++, K+, Na+ etc, they do. Also I know that if you want to kill an obligate hard water fish (particularly from Lake Tanganyika) really quickly you can try keeping it in soft water.

I don't much about fish physiology, but if you look at the paper <"Low pH and calcium effects on net Na+ and K+ fluxes in two catfish species from the Amazon River (_Corydoras_: Callichthyidae)"> it actually talks about the lack of calcium, and other cations, in the waters inhabited by _C. aldofoi._


> It is reasonable to propose that Ca2+ does not play any special role in blackwater fish acid tolerance since this element is almost unavailable in the ion-poor waters of the Amazon region. This supports the idea that ion regulation in blackwater systems is modulated by different mechanisms, as previously suggested by others (15,16,18,19).


 & 





> The adaptive strategies involved in acid tolerance in the blackwaters are still a topic of discussion. The physiological adjustments that allow fish to inhabit low pH waters with low ion concentrations seem to be their ability to maintain an ionic balance by a combination of adjustments to enhance transport and limit permeability. Most reports seem to emphasize the idea that ion loss control is the key factor for species survival in acid waters, rather than maintenance of the ion uptake rates. Naturally adapted fish from soft ion-poor waters such as the Amazon blackwaters did not show branchial affinity for Ca2+, indicating modulation by other still unknown physiological mechanisms. The investigation of the effect of dissolved organic carbon compounds on ion regulation should be a fruitful field for additional research concerning the natural adaptations of fish to naturally acidic waters.


cheers Darrel


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## sciencefiction (1 May 2015)

dw1305 said:


> Naturally adapted fish from soft ion-poor waters such as the Amazon blackwaters did not show branchial affinity for Ca2+, indicating modulation by other still unknown physiological mechanisms.



So basically it is not known yet how fish from black water environment utilise Ca2+? 
Then we can't argue either way.


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## sciencefiction (1 May 2015)

dw1305 said:


> <"Low pH and calcium effects on net Na+ and K+ fluxes in two catfish species from the Amazon River (Corydoras: Callichthyidae)">



It's a really interesting article. Non-black water cory tolerates a rapid Ph drop from 6 to 3.5 better than the black water cory 

There's another here about cardinal tetras quite capable of adapting to acid water conditions too. It seems some harder water species can adapt to ion poor acidic water.  Some "blacker" water species like clown loaches do quite well acclimated to harder water too. I've seen them even in African Cichlid tanks although that maybe an extreme.

http://www.researchgate.net/publica...lrodi_(Schultz)_subjected_to_extremely_low_pH


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## sciencefiction (1 May 2015)

There is a bit more on the studies on Amazonian fish and ion fluxes

_Several studies of ion fluxes between the fishes and their

external media were performed in samples collected from the

Negro River (Gonzalez et al. 1997, 1998, 2002; Wood et al.,
1998; Wilson et al., 1999; Gonzalez & Wilson, 2001) and some
demonstrated that they are more resistant to acidic waters

than those that do not live in black waters (Wilson et al.,
1999; Gonzalez et al. 1997, 2002). *However, only two studies
analyzed Ca2+ fluxes in Amazon fishes, and they were
performed with modified well water, which is similar to the

“clear water” (Wilson et al., 1999; Matsuo et al., 2005). In
addition, transfer of tamoatá (Hoplosternum littorale) and
pirarucus (Arapaima gigas) from black water to white water
or vice-versa induced only minor changes on net Na+, K+ and
Cl- fluxes (Baldisserotto et al., 2008), but Ca2+ fluxes were not
studied. In addition, waterborne Ca2+ uptake occurs much
slower than Na+ uptake (Matsuo et al., 2005).*_
*
More here:
http://www.scielo.br/pdf/ni/v7n3/aop0209.pdf
*


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## tam (2 May 2015)

sciencefiction said:


> Took a picture of a snail just now. All info points my snails shouldn't have calcium deficiencies in my hard water. The rest of the survivors are about the same size, some have normal appearing red shell, some white. Anyone venturing a guess why this is happening in a hard water tank? Water is changed at 50% weekly for around a year without a fail. The issue is just in the one tank with the same tap water as in the rest 4 tanks I have.



I don't know anything about snails, but if you've got calcium then I'd guess the issue would be they are missing something else trace wise they need to build their shell - like plants having plenty of one thing but be limited by something else missing. You'd have to read up on what snail need - humans for example need vitamin D along with calcium - in which case light could be your variant. Or it could be whilst hardness effects shell erosion, it's diet that effects growth and the food is different between tanks?


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## sciencefiction (2 May 2015)

Thanks Tam. The food is the same. Staple pellet I use is NLS cichlid pellets between all tanks.   I'd have to research what else they could be missing that this tank might not have. I have no idea right now. I suppose it's not an issue as I have plenty of snails. It's just that I want to know what causes it in this particular tank.


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## dw1305 (2 May 2015)

Hi all,
There is an explanation of why older snail shells whorls erode in this thread <"Nerite Snails in high tech..">. I think for the vast majority of people water with a reasonable amount of carbonate buffering is going to be preferable, and make aquarium management easier etc. 





sciencefiction said:


> There's another here about cardinal tetras quite capable of adapting to acid water conditions too.


I think you are going about this the wrong way round. The researchers are trying to find the factors within the physiology of Cardinal Tetra (<"_Paracheirodon axelrodi">_) which allows them to survive in the acidic, mineral poor black-water, they aren't *adapting to it*, they are *adapted for it*.

The paper indicates that humic substances (from the leaf litter) are important. There are plenty of <"academic papers"> on this subject and aquarists have also found this, in <"All the leaves are brown"> & <"Skeptical Aquarist  - Leaf litter">.

In the Cardinal Tetra paper it says that they have extremely efficient uptake of available cations (Ca++, K+ etc),  which may well be why they don't do well in harder water long term (they accumulate high levels of Ca++ etc, which then interferes with kidney function etc).

cheers Darrel


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## sciencefiction (2 May 2015)

dw1305 said:


> I think you are going about this the wrong way round. The researchers are trying to find the factors within the physiology of Cardinal Tetra (<"Paracheirodon axelrodi">) which allows them to survive in the acidic, mineral poor black-water, they aren't adapting to it, they are adapted for it.



Thanks Darrel. Yes you are right. What I wanted to say is fish can adapt. I am not saying black water species can adapt to hard water. Some fish have the capability, others don't.
I overlooked that cardinal tetras are actually adapted to it. I never kept these fish.  The corydoras schwartzi was a better example


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## sciencefiction (2 May 2015)

dw1305 said:


> There is an explanation of why older snail shells whorls erode in this thread <"Nerite Snails in high tech..">. I think for the vast majority of people water with a reasonable amount of carbonate buffering is going to be preferable, and make aquarium management easier etc.



This doesn't answer my problem though. What would you suggest to solve the shell erosion? I've posted my stats earlier. At least that's what the tests read but I've no doubt I have hard water coming out of my tap and it reads the same in the tank.


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## sciencefiction (2 May 2015)

sciencefiction said:


> Some "blacker" water species like clown loaches do quite well acclimated to harder water too.



Clown loaches come from very acid black water habitats from Borneo and Sumatra.
Many people keep them in soft water(RO mix) trying to mimic the conditions. If you search for "clown loaches black spots" you'll find numerous threads about this black/brown spot "disease" which is actually caused by a fast TDS drop(people adding freshly made RO mix water to the tank). The water is probably swinging the Ph too.  You would imagine them thriving in acidic conditions but as many other fish, stability is more important. I would imagine trying to keep any black water species is a challenge if they can't adapt to more "stable"/harder water tanks.
Here is an example pic I saved, with clown loaches kept at a Ph of 4.5, Kh 1 with an ever dropping Ph. Some don't survive these constant fluctuations they are subjected to in a tank. The issue seems to be resolved when the water is "stable" regardless of Gh, TDS, Ph, Kh, etc..






Other tank mates in the same tank:






And my clown loaches in hard but stable water.

I rescued this one  a year and a half ago looking like this when I got him.





Now


 

A video of him now. I dare say he's thriving despite me being told a few times I should keep them in soft water. But my stats are rock solid and don't fluctuating one bit except for the TDS rising by the end of the week but I dose some ferts too.


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## Andy Thurston (2 May 2015)

sciencefiction said:


> Soft water species are capable of utilizing low calcium/magnesium availability in the water. However, being the sceptic I am, one needs to know whether those people's fish lived their full life spans in whatever conditions they were kept in


 re: the clown loach.
They do seem to be looking quite healthy but are you going to live long enough to see if they reach their full lifespan potential in harder water?


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## sciencefiction (2 May 2015)

Big clown said:


> re: the clown loach.
> They do seem to be looking quite healthy but are you going to live long enough to see if they reach their full lifespan potential in harder water?



Yes, that's a valid question that gets thrown in a situation like this every time, which one I will only be able to answer in 20-50 years if I am alive myself. I don't know if they'll reach their full life span kept in this water.  It's yet to be seen. There are very few accounts of keeping these fish alive for more than 20 years regardless of the water in which they were kept. I can't do complicated tests on my fish to know if they are "adapted" to my water. But I know non-thriving fish develop all sorts of unusual "diseases" if not happy.
All I can say is based on colours, development and behaviour mine seem quite healthy for now. Time will tell. I maybe wrong.
If that sickly looking clown was not happy in my water conditions, he wouldn't have improved over time. He would have gone worse.  It took him about 6 months to "improve".


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## LondonDragon (9 Jul 2015)

Could you use TDS as an indicator for when you need a water change? I have noticed that it increases over the week, tested with higher levels of feeding and it increases quicker. My TDS comes out of the tap at 550-580, in the tank after a water change it adds another 100 or so. By the end of the week this usually increased to around 750-800, and resets back to 650-680 after a water change. Thoughts?


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## dw1305 (9 Jul 2015)

Hi all,





LondonDragon said:


> Could you use TDS as an indicator for when you need a water change? I have noticed that it increases over the week, tested with higher levels of feeding and it increases quicker. My TDS comes out of the tap at 550-580, in the tank after a water change it adds another 100 or so. By the end of the week this usually increased to around 750-800, and resets back to 650-680 after a water change. Thoughts?


Yes, that is really what I do. I just mix our tap water (about 17dKH) with rain water to give about 100 microS. Because I don't add nutrients regularly, but I do a lot of small volume water changes, after I've fed the plants, values will return to the ~100 microS level fairly quickly.

cheers Darrel


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## parotet (10 Jul 2015)

I guess if you are an EI user things may be more difficult. I learnt from Darrel the use of the TDS (as he says, cheap equipment, no maintenance, fast reading and quite reliable measuring) but I add daily potassium sulfate and micro mix... Dosing that lean I end up the week with 200-300 microsiemens more and I believe a significant part of them is due to the salts added. I have not enough skills to calculate this but it seems to me that adding 30 ppm of NO3, 5 ppm of PO4, 30 ppm of K and micros will rise your TDS quite a lot, isn't it?
I think it can work in lean dosing tanks as an indicator of.... Of what exactly? Metabolites?

Jordi


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