Black Moor Issue

[ApolloJ]

Hi, it seems my Black moor rests in the bottom of the tank at times...I wonder if there's something wrong, my two other goldfish are fine though, there's good filtration in the tank, but there's also a 6.5 cm pleco, I was told they shouldn't be put together, others said it was fine, so far I haven't seen any contact between the pleco and the goldfish at all, I do feed the pleco a lot of cucumber, so it seems impossible to me that he's sucking on the goldfish because of starvation, oh and it's a 20 Galon tank, any ideas why this is happening?

 

[aly_starh]

Well, to put it basically...... Your tank is way too small.
In a 20G tank you have 3 Goldfish and a pleco (which im guessing is common)

That the tank is only suitable for one of those fish, 2 if you have really good filtration, but thats pushing it.
The Pleco will reach 24" really soon.

So rehome 1 goldfish and the Pleco, and you will see a dramatic change in behaviour. The Black Moor could possibly be stunted.