I currently have a 20 gallon tank that has been running for about 2 months and it has been running very well. I have a black molly, a dubawi catfish, 3 cory catfish, and a baby bristlenose pleco. I am very informed in the world of fish and looking to get a new tank but i am debating the size of the tank. I am thinking a 55 gallon tank for a few ranchu goldfish or a 100 gallon tank for an oddball. I was wanting to get into breeding goldfish. I would need 2 40 gallon breeder tanks and a 100 tank for storing the adults. I will get into breeding another day though. So what tank would you recomend for me? The tank sizes above are just examples. Also if you could recomend any fish, that would be amazing.