possible phosphate problem?

[map95003]

Hi All,
My tank is 6 months old, 2 wks ago I replaced my T5 10K bulbs with ATI Aquablue specials and Blue + (6x54w), about a week after I started seeing signs of a thin layer of dark brown (almost black) algae on my sandbed, seems to be more in areas with less lights and flow, like closer to the base of rocks. I'm not sure if it has anything to do with the lights or if it's phosphate related. I've been using the API phosphate test kit and it's not very easy to read. Seems like my phosphates are always between 0.0-0.25, I can't really tell for sure. I just tested my fresh RO salt mix and it seems to read ~0.5, that doesn't seem right. Is there an easier way? Which phosphate test kit are you guys using with great results? Any other suggestions on the algae problem, also lots of air bubbles attached to the surface of this algae?

Note: my RODI unit reads 0 tds, my filters are ~5 months old.

All my other parms test OK.

PH: 8.1-8.3
Alk: 9.8 dhk
Ammonia: 0
Nitrite:0
Nitrate:0
Ca: 400
Phosphate: hard to read (looks like 0.0-0.25 /w API )

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[odyssey1]

It could verywell be the lights however there are other thing that contribute to this I would suspect high nitrate levels. This in conjunction with the liting change could do it.

I had a similar problem over a year ago. I added lights more in the red spectrium hoping to grow my corals faster and caused a bad algae breakout. I had to remove the lighting and add a denitrifier and low and behold my algae was gone.

Not sure you want to change the lights but you will need to check the nitrates to see if it is contributing. anything over 10ppm will cause problems.

 

[luther1200]

I had the API PO4 test kit and hated it. I was not very happt with any of there test kits. I now use a Salifert kit. Which is much better but still a little hard to read. But if you double all the amounts and use the low range, its much easier to see the results. But if your level really is as high as 0.25 thats a little high IMO. But not terrible.

 

[map95003]

would a few water changes help this situation...or would I just be masking the problem?

my total volume is ~110 gallong, I do bi-weekly 15-20g water changes.

 

[odyssey1]

It will help your water quality but wont fix the problem. You have some nutrients in the water causing the problem.

Just because your test kit reads low or 0 dosent always mean there is no nutrients in the water because the algae is eating the nutrients causing the low readings.

You will need to try more drastic measures than water changes. Get a phospate sponge or a phosban reactor or a GFO reactor to get rid of these nutrients. I would start in that order and give it time. If the levels are low like you say you may only need the phos. sponge. You also need to recheck the nitrates because this is what caused alot of my brown algae problems. I tried everything first then added a denitrifier and this worked wonders on my system.

 

[odyssey1]

Another thing you could try is a UV steralizer. If the algae is a bacteria problem it will help but keep in mind you have to have a pretty stable system because this will also remove the good bacteria.

Pics of this algae will help.

 

[map95003]

thanks guys.