<a href=showthread.php?s=&postid=8357636#post8357636 target=_blank>Originally posted</a> by Atticus
AAAACCCTTTUUUALLLYYY....
The 4 foot 20 gallon has the same surface area as a 20H.
The 30 gallon has almost double the surface area of a 29 gallon aquarium.
So, they actually are more than adequate when it comes to gas exchange.