Yea i agree and know all this just got dooped by the LPS fucks. ya know no research impulse buy. I do water changes very frequently the rocks are for a pregnant guppy just for now. He's getting his own 30 with nothing in it soon. I just have to get rid of this piranha first. I'm juggling fish lives it's not fun but a lesson well learned trust me. I'm on the verge of finding right priced glass to build a 125 gal. That should be more then enough for what I want. Then he can go in the 55 or a pond one day. We just got lied to over and over again :( my fault for not checking first.

yes I agree with stingray...the plycostomus will eventually grow to 7" and the black moor goldfish will grow to 10"...in a 15 gallon tank?

You need a good 75 gallon (50 gallon mininum) in order to keep these 2 fish happy/healthy.

As for fin rot, unless it's such a large tear, pay it little mind, it will heal itself. The problem is, the sore if it is open can get infected. Which in turn breaks down the fish's immune system or the fish does not have the energy to fight off the ailment, and this secondary infection is what will kill the fish or make it very unwell.

So my advice is, watch for secondary infection. Observe closely...and please please, in time, get a much larger tank.

Thanks for sharing