water quality?

Maybe something's gone wrong with my tank, or I did too many little things at once. I took out the piece of cuttlebone. I took out all the rotting ambulia stems and the worst-looking hygro pinnatifida. Pulled up all the micromeria brownei and replanted the tops (cut just below aerial roots). Planted a half-dozen extra pieces of elodea out of my daughter's snail bowl. Did all this in the same instance, but now I'm wondering if disturbing the substrate fouled the water some? A few of my fish have been flashing as if irritated- but they don't appear sick (I checked very closely for ich spots). Yesterday I saw the fishes still don't look quite right- lots of barbs have pale patches of skin and the females have awfully rosy cheeks. Water test still showed 0.25 ammonia and 40 nitrates. Not sure how to take this- are the nitrates up still because I disturbed the substrate? is ammonia showing just from tapwater- because I've had that occur in the past and turns out it wasn't a problem- prime makes the ammonia harmless but it still shows on the water test... Well I did another partial wc of 20 gal. Lots of spawning activity resulted among the cherry barbs, so they can't be feeling too bad.

Later in the evening I heard splashing. Have noticed this a few days in a row now- some time after the lights go out, I hear momentary dripping or splashing from the tank. I thought I had a leak, but no sign of that. This day it occurred several times in a row- finally I sat in front of the tank and waited for it. One of the striped kuhli loaches was swimming up the filter outflow! I got a view from above the second time it happened in front of me, and he darted up far enough to get bumped back by the turning wheel.

Now I don't know if the kuhli was trying to escape because of poor water? or responding to weather changes- we did have a large drop in temperature last night, and I've heard these loaches can get very active with changes in air pressure, including escape attempts! It was late, I was tired, I did what I could think of to prevent a fish getting out in the night.

I stretched a piece of netting- black bath pouf I bought for making subwasser baskets- over the filter outflow, it is folded like a 'u' under the lip of the filter so hopefully this will prevent the fish from getting up into the filter. I have it held on either side with clothespins which are tacked on the side of the filter box using a strip of duct tape. Very makeshift I know, and I worried about a fish getting itself stuck in the netting.

But I sat there another hour and it didn't occur again- maybe the netting baffles the outflow of water enough that it doesn't attract the fish anymore? I was relieved that I didn't find any loaches stuck in the netting in the morning or missing from the tank, but I need to find another solution to this. Maybe I'll lift off the filter box on maintenance day so I can fit the netting on there more tidy.