SPS slow grow

Growth directly corresponds with size. A 1" frag can take FOREVER to put on another inch, while a 6" colony can do it in ~2 months.

However, clearly your parameters are the limiting factors here.

In general though, SPS are pretty fast growers. That is their defense mechanism, grow fast to shade out other corals. (LPS grow slow but typically have sweepers and pack a much more potent sting than SPS). Typically, montipora capricornus and seriatopora hystrix grow fast. Just about any Acropora called a staghorn are considered to be the fastest out of the genus acropora, with some saying that acropora micropthalma (scripps staghorn acropora) is the fastest.

How is the flow to the acropora that are growing slow?

 

I try to direct flow from my power heads to make sure flow is strong enough for them. As you can see 8 months old frags on 1st pick are my concerns. Old Acropora on others pics are growing like crazy.. so does Montiporas. So when you say my parameters limit their grow then you mean ALK and MG, right? I will try to get them to the right point.

 

Yes. Also, raising phosphates to 0.5 will increase growth, with the tradeoff of thinner skeletons (in all hard corals).

 

O well, always something new... Over the years people told me to keep Phosfate at 0 is the goal for healthy tank, so I run GFO, SPS needs perfect water. Now you saying it should be 0.5? Doesn't 0.3 costs algae issues?

 

Well I'm not sure at what point does algae start popping up, but I've seen quite a few studies where SPS were grown under different PO4 concentrations. I assume this has something to do with the fact that coral itself is a symbiotic relationship between animals (the polyp/coral itself) and algae (why the corals need light). If you think about it, all algae needs light and a food source.

I can't recall exactly why, but the higher the phosphate level, the weaker/thinner the coral skeleton becomes, to the point where PO4 is so high, the coral cant produce skeleton, and dies. This is probably where the idea of 0 phosphates came about. However, recently (one study for example on reefbuilders) showed SPS grown at different levels of PO4, I believe 0, 0.1, 0.3, and 0.5. At 0, growth was slowest but coral was denser, at 0.5, growth was fastest, but less dense. Obviously this doesn't mean run PO4 at 1.0 (lol) but just that a little bit is actually good for the coral.

 

Thank you very much for your explanation and your time. Ill try to do some adjustments