Once those bichir grow they should fill it up - when I had 3 together they were so lively, always out swimming and chasing. Just watch them in a group once they hit about 7" as if they get into a breeding mood they start jumping - that's how I lost 2 before(even with a tight hood they found a way out!)
Yeah I was concerned the little ones might find a way out thru the gaps in the hood, which have filter pipes in both, so makes it fairly tight. Will keep an eye on them though, dont want any jumpers, or suddenly notice them scurrying around the floor
