Mikaila31's comments earlier are absolutely correct. I am copying over a video from another thread in this section because it so perfectly illustrates what I write time and time again: fish absolutely must be in a suitable environment or they should never be acquired.
You will note the three knifefish are darting around, up and down behind that filter. That is an extremely stressful reaction to having no place to hide from the light and each other. A fish that is by nature used to darkness and hiding places will always be highly stressed in a bare or brightly lit tank. The fish does not know it is "safe" from predators; it only knows what nature has programmed into it, that in such an environment it is highly vulnerable and likely to be attacked and killed. It will spend its hours fighting to get out of those conditions. Unfortunately, it has no escape. The health damage done to these fish from their time in such a tank cannot be measured, and will almost certainly cause trouble down the road and probably early demise, or it may bring out excessive aggression once the fish is in a more suitable surroundings.
And as auntkymmie pointed out in the other thread, the poor Clown Loach
is similarly highly stressed out, darting around due again to lack of cover and lack of companions; social fish like the loach must be in groups, 5+, there is no excuse. And understand, my comments are intended to bring this to light with the obvious video proof, as showing what will occur when these fish are subjected to inadequate housing. I am less concerned with temporary store conditions than I am over aquarists who think this is how they can "care" for these fish at home.
We as aquarists all have the responsibility to know our fish thoroughly, and be able to provide what they require before any consideration is given to acquiring them.