Where did I come up with that figure, hmmm?
Most sites actually suggest more than three feet.
http/fish.mongabay.com/species/Polypterus_senegalus.html suggest 40 inch long for a full grown
http/badmanstropicalfish.com/profiles/profile41.html suggest 48 inches
http/www.fishforums.net/index.php?showtopic=34889 our own fourm says 30, which are usually 3 feet.
sorry for my irrational thinking, as the exact number of 3 feet never came in, and everything else suggests a little more except for our very own site. I also keep peacock eels, which reach around the same length, and their minimum is 3 feet, so I was probably thinking about them. But I still say 3 feet WOULD be nice.
And yes, open hooded tank would be bad. Mine is near the surface quite often, (they breath through their lung like things. forget the exact name, check the lings for more.), and I think if they thought they saw anything attractive, it'd be *JUMP*, and then if you didn't notice in around 2-3 hours, it'd be a goner. Easily dead in your sleep. sorry mate.
and I wouldn't stick a bichir with any real type of algea eating pleco, but check out Queen Arabesues if you're hardcore on getting one. I also have a clown.... I'm unsure when he may get eaten... but every time my senegal gets inside the slate cave he gets headbutted out, and now that the queen is in there, he doesn't bother.