I've been admiring pea puffers for a while now. I have read that they should be in 5 gallons or bigger. Do they need that much for the space, or just for water quality. I've been pondering setting up a 2 gallon tank with a 5 gallon sump filter, so there would be 6-7 gallons of water circulating through. Do you think the 2 gallon tank would be enough swimming space for a pea puffer?