Ok need some expert advice. Just did a water change in my 20 gal tank. All parameters appear to be good API test kit, ammonia 0ppm ph 7.6 nitrite 0ppm nitrate 5. But now all my tetras and my guppy are hanging at the top of the tank. They seem calm, not gasping for air, some are chasing each other so not lethargic but still kinda different behavior than I am used to from them. We have two sponge filters and a bubble wall so plenty of aeration. What am I missing or am I just overreacting? Also, have some mystery snails that just floating at the top but they are alive and have been active off and on between floats. Tank has been a struggle to cycle but has finally seemed to be regulating in the last week with daily checks and weekly water changes that vary based on parameters between 25-50%.