TheNanoAquariumGuy

How about not a fish but an invert like a crayfish. You could also do cherry shrimp and keep a colony and not worry about hospital tank or anything like it.

What's your GH? KH? Ammonia test? If they are indeed dying they maybe making too much ammonia.

Yea, again I have boiled it in the past and nothing happened, and later I was told of the risk so I just don't, because it does make sense if there is an expanding pocket if air it could happen. But chances are it would just crack and not explode if boiled. So I just been rinsing them with hot running water from the sink and I haven't seen a difference, but then again I bought mine from home Depot so it has probably been in a hot Warehouse and dry for a long time, if one is collecting from outside there is probably a higher risk.

I have used mostly lava rock because it is cheap. My understanding is that red lava rock has higher iron content so it should help plants a bit on that end. However for aesthetics, I just use the black ones. The other major thing I was told (haven't experience it myself) but if you boil it, it could explode. So I used hot running water to clean it and to the tank it goes.

Would a pair of pygmy sparkling gouramis work? I think I have seen some videos on those on small tanks and making Bubble nest and taking care of their babies for a while.