phosphate creeping up and coral health declining

[xcross]

Hi,
I've been running a Biocube 29 for about 18 mos. When I first brought it up I had lots of trouble with nutrients. Finally I converted the back filter chamber to a sump by scraping the paint off the glass, removing all the Biocube filtration junk, added a small pile of LR rubble and a chaeto, and hung a broad spectrum grow light on the back to illuminate the algae. I also run bags of GFO an GAC which I place at the bottom of the sump in front of the opening to the pump chamber.

The new sump worked wonders. Even though its small, about 1.5 gal, it drove all the nutrient measurements to zero, and the slime algae disappeared within days. Today the chaeto grows out to a solid mass in the sump about once a month, which I prune back by 75% and sell to my LFS.

I keep just three fish, a pair of clowns and a green chromis, and they look healthy on a diet of about 1.5 g/day of frozen shrimp.

About a two months ago I started noticing some algae growth on the LR and my acro, which was growing like crazy and looking great, had pulled in its polyps. Since then it has declined steadily and bleached, probably nearly dead. Several of the soft corals, particularly the zooanthids and mushrooms have shrunk in size by half or two thirds. The zooas stay closed.

Today I measured the nutrient levels and found nitrates and ammonia still undetectable but phosphate at 0.08ppm. pH 7.8. I maintain calcium and alkalinity in the optimal zone with Randy Holmes-Farley's 2-part method.

I wonder if I've got too many corals for the size of the tank. I bought a package of softies from a supplier that included a couple pieces of shell substrate with several species and the mushrooms on it spread and nearly took over the bottom of the tank. I have tried to prune them but its been hard to do. I also have a torch LPS that has probably quadrupled in size in the past year.

Will too much coral cause problems? Is the phosphate level of 0.08ppm the likely culprit? Is there anything besides nutrients I should be looking at?

Thanks,
Chris

[tmz]

I don't think PO4 at .08ppm would cause those issues if the measeure is correct.
Allelopathy might be an issue or a buildup or change in other organics over time. Organic carbon is the nutrient we often miss since we can't really measure it but in excess it can harm corals. Good skimming and running gac and/or purigen can likely help with that issue. Running some plyfilter or curpisorb might also be helpful if metals are the issue.
FWIW, Personally, my aquariums are dense with mixed corals without issue. Certainly something likea sick leather could mess up a tank though.

What is the salinity,btw?

[bertoni]

The more common sources of phosphate are food and contaminated live rock. A living organism won't add any phosphate to the water column like that, other than by dying and rotting. I would guess that the phosphate is from the food, if the reading is correct. I might consider adding a GFO reactor.

[FIREFISHPAT]

Just let you know I'm in same boat as you. My Phosphate is 0.08. In my 90 gal. Running Bio pellents and added GFO and chaeto in my sump / skimmer.. I notice that my ro/di water was high with phosphate so I changed the filters and order New membrane. Check your fresh batch or tap and see if its coming from there.

[zigzag1]

The more common sources of phosphate are food and contaminated live rock. A living organism won't add any phosphate to the water column like that, other than by dying and rotting. I would guess that the phosphate is from the food, if the reading is correct. I might consider adding a GFO reactor.

+1 Well said. GFO is your friend! IMO it makes reefkeeping so much easier than 20 years ago.

[xcross]

I don't think PO4 at .08ppm would cause those issues if the measeure is correct.
Allelopathy might be an issue or a buildup or change in other organics over time. Organic carbon is the nutrient we often miss since we can't really measure it but in excess it can harm corals. Good skimming and running gac and/or purigen can likely help with that issue. Running some plyfilter or curpisorb might also be helpful if metals are the issue.
FWIW, Personally, my aquariums are dense with mixed corals without issue. Certainly something likea sick leather could mess up a tank though.

What is the salinity,btw?

I did let the salinity creep down to about 1.021. How aggressive should I be at fixing? I planned to use seawater for makeup until it is corrected but at a quart/day it could take a while.

Also I had a build up of debris which I am trying to solve with the addition of a powerhead. Skimming is inadequate I know, as I have been relying on the toy skimmer that Oceanic sells that fits in the first filtration chamber: http://www.oceanicsystems.com/products/biocube-protein-skimmer.php

Given what I've written so far, what should I do first, improve the skimmer or add a GFO reactor?

[Randy Holmes-Farley]

Replacing evaporation with salt water is a good way to boost salinity. :)

[tmz]

The salinity at 1.021 could account for the coral issues. !.0264 is th ocean average. Corals can't osmoregulate like fish can. Their internal sg is governed in larger measure by the surounding water .When sg is low water diffuses into them upsetting their internal chemistry.

[tmz]

If you want to go faster given the stress signals the corals are showing, getting sg up to near 1.023 via water changes with 1.030 water would move it up faster. Two 10% changes should get it near 1.023( 1.0227) .If the two changes are done several hours apart the fish should be able to adjust to the two less than .001 bumps without significant stress. You might also do a 3rd 10% change the next day to bring it to 1.0234. After that top off with with 1.026 water will get you to 1.026 eventually and very safely even at 1 quart per day.