High nutrient high Alk?

[SB Reef Lights]

I have run higher trates, around 5 to 10ppm for years with higher Alk, 11.5 to 12dKH. I have always seen faster growth at the expense of a little coloration. When I drop the nutrients down as well as the Alk, color becomes vibrant again but growth slows. Nothing else changes in the tank, lighting, flow, feeding, skimming, dosing etc... Just dropping Alk by cutting back dosing and reducing trates through a few water changes. If I raise Alk back up before nutrients I get tip burn. If I raise nutrients up with out Alk, coral growth slows and they start to brown out.

Curious if others are seeing the same results.

What I have been doing is growing out corals at the higher levels and moving frags to a low nutrient frag tank to color up and swap or sell.

Thoughts?

 

[Randy Holmes-Farley]

Yes, your results seem consistent with what many others see and theories about how these things work.

Many hard corals will grow faster at higher alkalinity as that appears to be the limiting factor for calcification.

If nutrients are low (and alk high), the growing skeleton may outstrip the ability of the coral to grow the tissue to cover the new skeleton and may result in burnt tips.

Higher nutrients results in more golden/brown zoox, so corals are more brown. Lower nutrients means less zoox and better colors.

The two stage plan seems appropriate if the goal is to maximize colorful frag generation for selling.