TDS and Discus Fish

[Mr Wild]

Does anyone know if a really low TDS will have health effects on discus fish? My meter is telling me it is 12ppm in my 100litre tank and 51ppm in my 325litre tank. I beleive the results as I have just changed the water and we have had massive amounts of rain recently so my tanks are full to the brim with fresh water, usuually the TDS is around 100.

I am now adding flex discus minerals when I do a water change but I notice the fish lag, for want of a better word after wc's. So I am wondering if this could have this effect.

PH 6.4
Ammon 0
Nitrite 0
Nitrate 5 (usually 10 but as I said just done wc.)

Any opinions?

[KDodds]

How low does your pH kit go? If it bottoms at 6.2 or higher, there's a pretty good chance that you're not getting accurate readings when (if) pH goes lower. As I mentioned in your other thread, 12ppm is extraordinarily low, almost pure water. This is not necessarily good for fish, even "soft water" fish like discus. Buffering is almost non-existent and osmoregulation can become a problem (physiological stress) for the fish. As well, since you now mention the drop happened with the water change, and it's such a drastic drop, you may have solved your problem. You might want to consider mixing in some RO "reconstitution" product to raise GH/KH because what you have now is, essentially, a step away from being RO. In fact, some RO units on some water supplies, will produce water with low double digit TDS consistently, after producing only a few gallons. Anything below 20ppm is still really usable as "RO" in most cases, once it goes above that, you really want to think about replacing your membrane (and possibly the DI cart, if you have one). Anyway, digressing here... I think most folks are keeping their discus in whatever they have OR, if shooting for a target, are keeping them at or around a TDS of 100ppm.

[Mr Wild]

Oh thank you finally I may have some answers. What sort of product would I use? I have never heard of anything before as I have never used RO water. I have always struggled with the idea that is was too low yet I have asked questions before on others sites to no avail. Perhaps you have got it ! I do hope so, please advise what product I should try and I will get some asap. Thank you so much and keep everything crossed! Kath