Yes, that’s a temptation we plan to avoid, which is why we’re trying to introduce most fish that we want now. I’m going to have to do some fiddling until the water’s right, though, because we really want more neons. The last time I tested it, the PH was high and the nitrate level was high, but a high PH is a peril of our hard water, and I’ve had neons before. High nitrate levels cause some problems, but don’t make the water toxic. Unless tetras are especially sensitive to it, but I haven’t seen anything that would so indicate.

What size tank is it? Many years ago we had fish but I could never stop fidding, never stop hitting the stores and buying just one more. And the key (as you know) to fish is setting up a tank and then not mucking it up with the introduction of new bacteria, fish, whatever.