solution

[Pauper]

I have a SPS tank with the following parameters

Temp 78 to 84
PH 7.9 to 8.1
Calcium 320 ppm
Magnesium 1220 ppm
Alkalinity 5.6 to 6.4 dKH
Phosphates undetectable
Nitrate and Nitrite 0

I have what looks to be either a hair algae or blue/green cyno problem. It is growing along the back corner walls and I can't seem to solve the problem. I only use Kalk and don't dose anything else. I do about a 30% water change monthly. I know my Alkalinity is low but can't seem to move it up and I wonder if that is causing my problem or if my problem is causing the drop in Alkalinity.

[jansenwrasse]

The PO4 that you are not showing on test kits is most likely bound into the hair algae that you see in the tank. Snails and fish eating it will release the PO4 back into the water for the algae to grow somewhere else or into a larger clump. I would start to use a GFO based PO4 remover to "intercept" the cycle.

Good Luck!

[Randy Holmes-Farley]

The calcium and alk are low and you should supplement more until it stays at least at 7 dKH alkalinity and 360 ppm (preferably 420 ppm) calcium. I'd also boost magnesium a bit, to 1250-1350 ppm.

I do not see anything that particular is a cause of algae problems, but reducing nutrients typically helps if done adequately.

These have more:

Reef Aquarium Water Parameters
http://www.reefkeeping.com/issues/2004-05/rhf/index.htm

Phosphate and the Reef Aquarium
http://reefkeeping.com/issues/2006-09/rhf/index.php


The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 1: The Salt Water Itself
http://reefkeeping.com/issues/2007-03/rhf/index.php

The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 2: What Chemicals Must be Supplemented
http://reefkeeping.com/issues/2007-04/rhf/index.php

The "How To" Guide to Reef Aquarium Chemistry for Beginners, Part 3: pH
http://reefkeeping.com/issues/2007-05/rhf/index.php

The “How To” Guide to Reef Aquarium Chemistry for Beginners,
Part 4: What Chemicals May Detrimentally Accumulate
http://reefkeeping.com/issues/2007-09/rhf/index.php