[Wiskey]

Well,.. The more you have, the faster it can (potentially) increase in volume, and the more phosphate it can remove.

But there are other limiting factors. In a sump you are only lighting from above, which means only the top few inches are getting enough light to grow effectively. In a reactor it is being lit all around the algae. CO2 is also often limiting, and more importantly how effectively CO2 gets to the plant. Most sumps are very slow flow, and because water produces a substantial boundary layer around plants this would effect how much CO2 they can actually get. In a reactor with high flow going through it this would be less because the flow would decrease that boundary layer. You could do the same thing with powerheads.

That being said, I think there is more at play here than the amount of algae.

It's also worth noting that I've seen references to where Phosphate becomes limiting to algae being around 0.03. This is my target for P04 in my tank, and I think it tends to indicate that it's impossible for algae to reduce p04 so much that it would limit or bleach corals alone.

Whiskey

 

[Wiskey]

My cheato is actually getting more PAR than my SPS coral. There seems to be no upper limit, at least not one I've found.

Still though, it was not enough to keep my PO4 down long term. Though it surely helped, it depleted my N03 faster. It's growth took an uptick when I started dosing NO3 but I had to add Phosban anyway because I struggled to keep it below 0.1 without. Now I'm down to 0.03 where I should be in an SPS tank. I'm still dosing NO3. Interestingly my Cheato is still growing (though slower) which leads me to believe that I at least have periods of time when my PO4 is much higher.

My Acro growth has taken an uptick since lowering PO4 though, and the color is coming back.

Whiskey

 

[Wiskey]

Old thread, but I've done this!!! The one I chose wasn't great and they kept failing every few months, but as far as growing Macro goes, it does work! I think Tunze makes one for this purpose now, if I were to do it again I'd use that one. In fact I might use that and underlight my traditional refugium as well as the overhead light one day to see if I get better performance out of the algae.

Whiskey