New (65?) gallon tank!

[Collinsmomma]

Hey everyone!
The move went good with getting my cousins tank and fish. We think the tank may be a 65 gallon, but dont know how to tell. We are not sure of what the fish are, except for the big Jack Dempsey. We need help identifying them. He has had all these fish in the same tank for 5 years now since they were babies. Also it came with a stealth pro heater that he has had in there for a few years now, but we just read that there was a recall on those heaters. What should we do about that? Should we get rid of it? What type of heater should we get? We have a friend that is a member here with experience coming over today to help us out, but we just wanted to get some other advice as well.
Thanks so much!

 

[MC.Arowana]

i think one moorii, and i think 1 Maingano? the other one idk

 

[Collinsmomma]

here is another shot

 

[deeda]

Measure the L x W x H of the tank and divide that number by 231. That gives you the nominal gallons of the tank. A more accurate measurement is measuring the internal dimensions of the tank following the same formula.