Tank Troubles

[capper]

We have 6g, 16g, and 46g tanks. Our 6g tank houses 4 platies. They always have seemed quite happy and active. Last week we changed the substrate from a basic stone type to a soil substrate. Over the past couple of days I noticed them extremely quiet and hiding in a rear corner of the tank. Today I did a water test and noticed that the PH was about 6.5. It had been 7.6 or 7.7 previously. The substrate had a major impact on the PH level and likely has caused problems for our platies. I did a 1/3 to 1/2 water change and got the PH back up to 7.0. Our tapwater here (in Tokyo) is about 7.6 or 7.7. Any suggestions as to how we should proceed? I was hoping to move them into one of our other (larger) tanks so that I could have a small number of guppies in the 6g. However, guppies preferred PH is about the same as platies. Is there anything I should do to raise the PH if we plan to keep these type of fish in the tank?

Second problem... Our 46g tank is a community tank with several tetras, platies, African Lampeyes, a pleco, a few cories, and lots of shrimp. We have 12 Cardinal Tetras and have had them for quite some time. Suddenly today we noticed one is very sick and near death at the top of the tank. I did a water test and everything seemed normal. The ammonia level was a tad above the 0 level. However, all the fish seem healthy and fine. Any suggestions? I know that Cardinal Tetras prefer a lower PH. However, I was previously advised that they'd be fine in 7.5 or 7.7 water as they could adjust. Besides, we have other fish in there with slightly different needs.

 

[Seleya]

How does the 6 test otherwise? Is it possible changing the substrate threw it into a minicycle? That would account for the hiding. I would be careful of larger water changes in this tank so the fish aren't subjected to major swings. The rest of your tanks have the higher pH, correct?

If the cardinals have been fine up to now and you see no obvious signs of illness, it may simply be this fish's time. Watch the tank closely, especially the other cards, but if everything is testing normally it may just be this one fish. Cardinals can adjust fine to that pH -- they may not breed in it, but living in it as long as the pH is consistent and the rest of the parameters optimal should be no problem.

 

[capper]

Otherwise, the 6 tests fine. The platys seem to be okay once again. I think you're right that the changing of the substrate caused some trouble with the water. I'll keep my eye on them for now... Thanks...