it is an old 20gal...had it for years...couldn't find dividers for the 55gal that they were in so i had to do this...they killed eachother...i lost 1 of the first pair i got to the other killing it...then got 10 more, 3 died from shipping, 2 got kill from one, then 2 more got killed from another...that leaves 3 from the 10 and 1 from the pair...for a while it seemed no matter what i did i woke up to dead aros...the last aro death was one that didn't eat...all the egg sacks got broken by the first agressor...the agressor and 2 more live on...