I agree with the others regarding biolode, nitrates etc. Very valid points. For me personally it's much more basic than that, ie give the fish a bit of room. These are pets not prisoners. I get it, all tanks are restrictive, they are not rivers. I do however feel we should be as fair to them as we can.
Anyone can do daily water changes and keep water pristine but that won't expand glass walls.
Fish need stimulation and exercise, and for me that's as important as keeping nitrates low.
The fish tank size debate for a particular stocking is a long winded debate with many differing opinions.
My moral compass points to these questions.
Can the fish reach full speed in my tank?
Can the fish make a home(territory) within the tank and still have other parts of the tank to explore?
Can the tank allow tank mates to coexist without aggression?
In reality I think just looking at a tank that is too small for its occupants is very clear to see.
I just say to myself, are you guys really happy in there? No need for test kits to make a moral judgement call.
