I didn't know if I should post here or the Equipment forum but here is my question:

I plan to plumb my 40G breeder and my 54G corner tank into a common sump. The two tanks will be side by side and not seperated by more than a foot or so. In this case, will there be enough light coming from my 250W MH light used in my 54G Corner to light any macroalgae I will try to keep in the 40 tank. Note: this 40G will not be a complete refugium but it will be a lionfish tank (dwarf) and plan to grow macroalgae to help with filtration and make it look better without having to clutter things up with a light.

Is it possible to keep perhaps Chaetomorpha, Kelp, Eelgrass/Hairgrass, maidens hair and similar macroalgae with just the leak off light from my MH pendant. The pendant is about 12" off the surface of the tank so there will be a moderate amount of light coming off the 54 corner only about 12-15" away.

Well, it's definitely worth a try... I've kept chaeto alive in a dark sump with only lighting from indirect sunlight. Macro algae isn't hard to come by so I'd say to try it, if it starts to die it won't hurt to add more lighting.

It's possible, but would have a negligible impact on filtration since they'd be growing so slowly.

Probably not the grasses which require higher lighting IIRC. Also, I like what organism said.

So organism:

If I add a large amount of kelp or chaeto to begin with will the filtration be good. I think this is kind of rhetorical because I read that the filtration occurs as the algae grows but I might be wrong so no harm in asking.

Fosi:

I really dont have to keep macros, it can be a plumbed in FOWLR, I was wondering if it was worth the effort. I think it could be so Im going to give it a try.

That would probably do more harm than good, if you put in a large amount of chaeto the chaeto that isn't getting any light will die and flush the nutrients into your tank. You can easily get a little clip-on light from home depot with a 2500k bulb that will take care of your fuge.

I don't know what you mean by kelp, but I wouldn't put any kelp in there. If you mean caulerpa I'd avoid that as well.