Help - Silver Dollar With Hole In Side (Pics)

I'm hoping someone can help me with this one.

I've got a 225L tank - well established... had it for some years now. It's all in good condition and the water parameters are fine and all fish are healthy... apart from one.

One of my large silver dollars appears to have developed what looks like a hole in his side. I'm completely at a loss with this. I thought it may have been fungus - I put some salt in 2 days ago, and it does seem a little better... but it's still not good. The photo i've attached is one i've just taken.

Now, i'm wondering whether he's been attacked. His tankmates are:

1 other silver dollar of the same size
3 small silver dollars
2 large silver sharks
1 angelfish
1 common pleco

Could the pleco have done this? The reason I ask is because the silver dollars LOVE the algae wafers I put in and I have seen the pleco come out and see them off so he can have one.

Would appreciate any advice.

That does look suspiciously plec like. You do get the occasional 'rogue' plec that develops a taste for other fish's slime coats. Nothing for it but to rehome him with smaller, less flat bodied fish I'm afraid.

The silver dollar should make a full recovery, if you keep the water quality tip top.

I feel I should point out that your stocking is unsuitable, both in numbers and compatability, and for the size of tank you have.

Thanks for your reply.

I realise my tank is a little mis-matched, but up until this incident, all has been well for a long time - and I keep on top of the water parameters etc.

So you think it is the pleco then? Why would he do that - do you think it is a fight for food? I generally only feed the pleco algae wafers and cucumber - should I be giving him something else? Or do you think it's just a fight over the food i've been providing?

I've attached a pic of the culprit pleco

No, I don't think it's a fight over food; as I said, some plecs just develop a taste for the slime coat of other fish

I think it was the plec. Make sure to be adding salt when necessarily and not overdosing. Also you could try and give your silver fish a salt bath.

If you want to give him a salt bath fill a little tub or bucket with aquarium water. Add some salt. Than put your fish in a net and lower the net into the water. Keep your hand over the top of the net to make sure the fish doesn't jump out. If the fish struggles, stop and place the fish back into the tank. If it doesn't repeat this process 3 times a day. Leave the fish in the bath for however long you like, just make sure your hand is over the net at ALL times. Leave it in the bath no longer than 2 minutes.