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Hello, following the loss of my female L200, I realized that my pH was fluctuating too much. It is usually quite low, around 5.3.
My tanks all run on non-remineralized rainwater (except my shrimp tanks) and I haven't had any problems so far.
Last night, I discovered that my female L200 died. No matter how hard I looked for the reason, I couldn't find it: she wasn't skinny, no parasites, not old, in short, in great shape. So I test the classic nitrites, nitrates, ammonia... nothing. I decide to test the pH anyway. I knew in advance that my drop tests do not give results below 6. In order to confirm my hypothesis, I have it tested at my work where the pH meter is calibrated every day.
3.61 is the pH value that was found.
I am doing an emergency water change in order to quickly (but not too quickly) raise the pH with tap water (in which I put a water conditioner because of the heavy metals) which has a pH of 7.5.
The problem is that I would like to continue shooting on rainwater. I have the 8.5 sulawesi salt on hand but this one is very expensive and not necessarily suitable for Amazonian fish.
What remineralizing salts do you use?

I tried preis salt but this tends to lower the pH, something I don't want. Above all, you need one that increases the KH in order to stabilize my pH.

My tap water is extremely low in dissolved anything. I started using Seachem Equilibrium to buffer my water and keep pH swings from happening. I just add a pinch with a water change. Between that and having a reliable heater and thermometer the tank improved. Plants are happier and fish losses, especially with the dither schools, are extremely rare. The nice thing about Equilibrium is it doesn't have sodium.

Hi kiwidu21,

I'll be honest; I'm ambivalent about your plan to remineralize the water. I haven't kept , so I don't know their water needs. But when I've collected fish in rivers around Iquitos, the water's TDS was down around 20ppm and the pH was highly variable, from 3.5 to 6. I've always been taught that since pH is a balance of acids and bases, then in really soft water, large pH swings represent relatively small changes in [H+] concentration, so extreme pH values in very soft water is usually not something to try to fix. For example, I'm keeping and I used to keep at pH 4, and both were breeding under these conditions. The Dekeyseria water is a blend of tap water and RO water, with a TDS falling below 50 after water changes. (I do 80-90% water changes). The Corydoras water was harder, but still under 100 after water changes.

I'm concerned that your remineralization efforts will cause more trouble than they will solve. So please be very careful. I hope you are successful in keeping your L200 healthy.

I think this would be a good topic for Darrel to chime in on (@dw1305).
Good luck!
Eric

I am skeptical of "remineralizing." I have a chart of tap water/rainwater mixes capturing pH and GH from 90% tap and 10% rain to 90% rain and 10% tap. Works for me. I would never do 100% rainwater except to hatch very sensitive eggs. Just too easy to crash the pH.
-Shane

So does this kind of variation exist in nature? Because from 6 to 3 seems huge to me.
If that variation isn't the cause of death, I'll have to keep looking.
In fact I don't want to completely remineralize the water, my other tanks run on rainwater without remineralization without worry. It was only on the hemiancistrus tank that I noticed large variations in pH. I am mainly looking for a way to stabilize the pH (therefore increase the KH if I understood correctly) to limit these variations.

In our tanks, we need to buffer the pH. Most often we do this with CO2- carbonate buffers, but under pH = 5 these so not do much.

In nature, the very size of the waters also helps buffering the pH. A dead cow will spoil quite a few cubic meters of water - but not a river. I think that is why fishes form very acidic waters are so hard to keep.

Once I heard of someone who had a canister filter filled with peat, and this peat did the buffering for him. On one hand I can understand that this works, but on the other - the minite the filter is clogged, the buffer stops working

A shift from 6 to 3 is huge. That is, the concentration H+ went from 1 in a millionth to 1 in a thousanth. An that will have a large influence on the skin and, more importantly, the gills.

You can remineralize, but natural contents of minerals in Amazonian waters are low. Extremely low. So low that these minerals will not be able to buffer anything.

Perhaps you can try with the peat canister? Use half fresh and half used peat in order to have a appoximation of the ideal buffer - half HB and hald B- - HB stands for peat with H and B stands for peat without

Peat will not help lower the pH?

Honestly, just go out to your local fish restaurant, enjoy a dozen oysters and ask to take the shells home. Keep the shells in the rainwater; they will slowly dissolve over many months. Keep a few in your tank too. This is a slow-burn solution to an issue I have too, the beauty of which is that as long as you move water regularly every couple of weeks, nothing goes too high or changes too quickly. Once you get a feel for it by measuring pH (you don't need to bother with dGH), then you can pretty much do it by eye (adding shells).

The issue is as much the range of pH as well as the time it takes to change from one value to another when water is changed.

Jools
PS Limestone, most marine invert shells will work too. I avoid things like crushed coral, but they will work too.

Hi all,

kiwidu21 wrote: ↑07 Jul 2023, 13:32Hello, following the loss of my female L200, I realized that my pH was fluctuating too much.

bekateen wrote: ↑07 Jul 2023, 20:59 I think this would be a good topic for Darrel to chime in on (@dw1305).

The first thing is to say I'm sorry for your loss, but I'd be very surprised if it had any connection with pH variation. As Eric (@bekateen) has alluded to pH and pH stability are quite problematic and you can't extrapolate from hard to soft water, basically if you have very soft water, the pH will never be stable and it doesn't matter. Unscrupulous vendors have exploited this conceptual difficulty to sell pH buffers etc. I think buffering may be relevant, but purely that in very soft water I like some tannic or humic substances, and these may help with fish health and mineral balance <https://www.nature.com/articles/s41598-020-80449-0>.

Personally I do the same as @Shane and @Jools, I just add a nominal amount of carbonate hardness via tap water (about 17 dGH & 17 dKH) or Oyster shell chick grit <https://www.planetcatfish.com/forum/viewtopic.php?p=310705&hilit=oyster+shell+chick+grit#p310705>.

Rather than being too worried about pH values I look at all changes in terms of the changes in the chemical composition of the water. In hard, alkaline, water you need a large change in chemical composition to change pH and in soft water very small changes in chemical composition cause large changes in pH. This pH variation is often a "diel" variation between night and day as the relative proportions of dissolved CO2 and O2 cjhange during photosynthesis <https://www.planetcatfish.com/forum/viewtopic.php?p=327425&hilit=Diel#p327425>.

kiwidu21 wrote: ↑08 Jul 2023, 05:39So does this kind of variation exist in nature? Because from 6 to 3 seems huge to me.

It does, in fact in very soft water you can get much bigger pH swings than this. <"https://www.ukaps.org/forum/threads/a-question-dissolved-oxygen-and-a-pond.58304/">

This is the Rio Tapajos (a clear water river, with very low conductivity), and even though we don't have pH values from the video, the amount of evolved oxygen (you can see the "pearling") will have driven the pH up to ~pH10. The base pH level will depend on the level of dissolved CO2 and the amount of humic compounds, but I'd guess just before day rise it will be well below pH 7 and possibly as low as pH4.
cheers Darrel

kiwidu21 wrote: ↑08 Jul 2023, 09:35 Peat will not help lower the pH?

If you use used peat and new peat in a 1:1 ratio, than you add a buffer. The pKa of humus - that is peat - is around 4.5. Therefore the buffer will try to get the pH at that value

the trick is in the used peat. That will be revitalized if the pH gets under this value, and then it works as a base.

Basically the same as a CO2 - HCO3 buffer does, but at a much lower pH value

Thanks I will test