We only got 1 just see if it would suirvive
Right. But your OP said you “tried everything”. Plants, snails, chemicals etc.
I’m letting you know that you plants will work if you use more of them. But they have to A) shade the water and B) be present in sufficient quantity to utilize all the “plant food” that the fish and snails. make.
if the plants leave sufficient light and nutrients. Algae will utilize them.