What are you using to test your water?
The only tests most here on Fishlore recommend are the
API tests. These are available in a API Master
test kit for freshwater, at most stores. The kit is cost effective since it provides ample testing chemicals to do hundreds of tests.
I am seriously concerned for your tank. It is 3 months old, and you have only 55 gallons, stocked with almost 100 inches of fish.
Even if they are babies now, we count the fish in "Adult inches", with the rule of thumb for stocking 1" per gallon of tank.
I assume the synodontis cat is the "upside down cat"? That is one of the smallest synodontis cats, so that is what I counted....if it is one of the larger ones, they could grow almost a foot apiece!
Bala sharks grow to 14" each, and need a long tank at least 72" when they are adults.
Hatchet fish should be in schools of at least 6, they will not live as long in fewer numbers.
The bio load in your tank is causing stress, which would predispose your fish to infection.
I can't account for why you don't have any nitrate readings at this point. IF your tank is cycled, you should have nitrate readings. By changing 25-30% water every day to two days, you are keeping your fish alive, but it really doesn't sound like the tank is "safe" at this point.
My suggestion would be to get another tank of AT LEAST the same size, and split your fish between two tanks, and use bio-spira in each tank to jump start the cycle. Then you shouldn't do water changes for a week, let the bacteria multiply, then you should be fine with only one 25-50% change every week.. It will cut the work for you, the stress for the fish, and you will have some time to look for that really big tank your balas will need soon! Hope this helps, and Good Luck
