Canister type design

Is there any reason why a canister filter type design wouldnt work? I read somewhere how the algae shouldnt be submerged in the water but rather needs the water flowing over it.If so what is the reason for this? I had made this design which I was thinking of using. It is highly energy efficient(not space efficient) and can also be sealed. I was also thinking of several other designs based on wet/dry trickle fitlers.
I have attached a design. It can seal by gasket or simply overflow into the tank.

A few people have built these, but the screen cannot be under water. Have the water enter from the top, in a circular pipe, and drain down to the bottom. Algae needs rapid flow, mixed with air, with lots of light, to grow fast.

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Originally Posted by SantaMonica

A few people have built these, but the screen cannot be under water. Have the water enter from the top, in a circular pipe, and drain down to the bottom. Algae needs rapid flow, mixed with air, with lots of light, to grow fast.

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Cool this is exactly where I am curious. What does the screen being under water prevent? Is it mainly the oxygenation issue? If so couldnt I inject air via venturi and have the unit overflow into the sump? Reason why I am pushing is because my sump is rather high and I dont have a lot of room. I also am using a lot of my sump already. I have plenty of room around my sump under my tank so fitting in a overflow style or canister style will work really well for me if it can be pulled off.

That would still be a prob. Every time light strikes an interface surface a substantial amount reflects back. Like 20%. Now how many air water surfaces do you suppose a froth of bubbles would have? It would likely be dark against the screen.

Consider a horizontal screen.

Do a low-profile scrubber like mine; only 6.5 inches high.