Fish staying to one side

So I know this is asked frequently and there surely is a thread already present for it, but none of the advice there worked. Hence a new thread

So my fish (4 gold, 4 gouramis) always seem to be at the right side of the tank. I thought it might be the heater (its at the left) so I shifted it to the centre. Didnt seem to work. It was maybe the knife in there but it got rehomed and still no effect.
1. Can it be that there's more oxygen on that side? (because I have more airbubbles on that side than the left)
2. Or can it be some rotting material? But I never feed on that side.
3. Theres an opening oyster that gives off a big bubble. Can that be scaring them?
I haven't vacuumed the gravel because I'm still cycling.

 

First off, how big is your tank and what are your water parameters? Goldfish can only live with other goldfish and bristle/bushy nose plecos to be safe. If anyone wants to challenge me on that opinion just say so and I will explain why. Pictures would really help. It's most likely that they are very overcrowded and bad water quality. IMO cycling is 20 times easier when done without fish.

 

Its 30 gallon (ik small) but ive been changing water daily.
Dont have water parameters but the water should be the same in the whole tank right?
They are with goldfish.

 

You need a liquid drop test kit to check your water parameters. And again, you need to rehome the goldfish or get a 75 gallon tank. You can keep the gouramis if you split them in the 30 gallon and get another 20 gallon.

 

It the clam thing that releases the big bubble. I used to have one of those pipe decorations they sell at pet stores and I put an air stone in it to make it look like it was active but it just scared the fish because the bubbles would get stuck in it and it'll release all these bubbles of different sizes. If you get rid of the clam I'm sure they would start swimming there.