would it be evil to downsize my tank
I have a betta and 6 pygmy corys in a 45-47L tank, this was my FIRST ever tank and its about 3 months old? everything has been absolutely fine however, something is off in my tank and I really don't understand what it is, all my duckweed died over night, the water is cloudy and the tint from the almond leaves just completely vanished, and I've noticed 2 of my corys acting odd. They'll swim up for air then come back down and be on their back on the ground and just not move, but if you disturb them they just swim off, and do it again a minute later, admittedly I panicked and I put those two in my mum's tank cause I thought it was a swim bladder issue (my mum's tank is shallower)
I use root tabs, flourish, the water parameters fine I think (ammonia <0.02, nitrate 0ppm, nitrite 0ppm, ph around 6.5), the ONLY thing different about the tank is I added some extra sand (washed) to just replace the sand I lost during a water change, so I expected a bit of cloudiness from that but not this much
Not too long after I started this tank, I got confident and made my mum's tank (has a female betta), the tank is smaller than mine, around 25L but long and shallower, and that tank has been better than mine in every way possible, so I'm not sure what I'm doing right and wrong on either tanks here..
I'm thinking I bit off more than I could chew as a first time fish keeper, which is why I wanted to ask, is it okay to downsize to the same size tank as my mum's, just till my corys are better and I learn how to better manage larger tanks :(? maybe even setting it up so my corys are in this tank and my betta is in the smaller one?
Also if you know whats going on with my corys please please any advice would be amazing