Thanks to both of you! I did go ahead and do about half the gravel with the last water change. I also added a submersible air filter and since then all the fish that had hovered at the top no longer do. So far I'm keeping the nitrites under .25 ppm doing 50% water changes (two so far).
One advantage of the salt is with nitrite; salt does help the fish handle nitrite in their bloodstream. The Prime should detoxify it before it gets into the blood, but still good to know.
No ammonia whatsoever since last night (when I started seeing nitrites climb). There is a ton of flow in the tank (bubbles everywhere) though I have the submersible filter turned upward but it still provides a lot of aeration. To clarify it's a 170 gph water pump with aerator. Is it possible to have to much aeration in a tank? Or possible to stress the fish with a lot of air flow?
In this situation the answer to both questions is no, within reason of course, since we are here dealing with major problems and increased water movement will keep oxygen coming into the water and CO2 leaving the water, and this is good. I don't think you need to go beyond what you now have running though.
Under normal circumstances, in a balanced healthy fish tank, yes, too much air flow/water movement can be very detrimental, depending upon the fish species. Some fish occur in fairly fast-flowing streams, so a river habitat with a good filter flow will mean happier, healthier fish. But with fish from ponds, swamps, quiet forest streams, this sort of aquascape would be debilitating for such fish like gourami, betta, discus, some characins, etc. These type of fish are usually not active swimmers, and like to quietly cruise around the tank, and fighting water currents takes energy and wears down the fish. I'm being very general here, obviously; there are several factors in this question, but I just wanted to give you a basic understanding. This is one aspect of a fish's habitat that the aquarist must understand since not all fish can manage the same in any tank. But dealing with health issues and nitrification takes precedence and it will be short-term.
They do seem slightly more active (the gouramis actually are not in constant hiding) now, but I don't want to stress them further so I'm keeping all the lights off except for when I absolutely need them on. After seeing your post I did go out and pick up some battery pumps, just as a last resort if the generator failed or something ceased to function correctly. Probably never need them, but better to be safe than sorry. On the whole even with all the issues and deaths I'm glad I was given the tank. I find fish fascinating (but never had the space for them previously till I bought the new house last month). So I have to admit, I think I might be addicted to fish lol. Even though they aren't very active/doing all that much, I still watch them for hours. You come to care for them surprisingly fast!
Nothing beats a water change. At the first sign of trouble, usually even before I have diagnosed what it might be, I do a major water change. The fish always respond positively. I think you're on the right road, and although some fish may not be able to make it through, you will get there and hopefully with most of them.
Byron.
