Light brown on sand

rbell219

rbell219

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Nov 12, 2005
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What is it and what causes it? It's light brown in color, but does not look slimy. It "glues" the sand together on the surface. When I stir the sand, it doesn't like to move.
Ph-8.3
Alk-4
Amm-0
Nitrite-0
Nitrate-goes from <5 to 10 during the two weeks between water changes
Calcium-420
(this stuff grows back within 3-4 days after water change)
 
It could be a diatom bloom if your tank is fairly new this would be normal. If your tank is established then my guess would shift towards cyanobacteria. Does the "brown stuff" float when you stir the sand? Any chance of a pic?
 
It doesn't float for long...and the tank isn't really new. Here's the story. The established tank was moved from my cousin's house to mine in Aug---5 miles. Then it developed a leak in Sept--so everything was moved again to a new tank<--this time I added all new sand---that Bio-Active live stuff. Both times I did a 30% water change and I do 20% every two weeks.
I'll get a picture this evening. Aslo---I added a 100 ml bag of Purigen in hopes to help eliminate Nitrates. Doubt that's causing it, but I left that bit of info out earlier.
 
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Its probably a diatom (brown algae) bloom. I used to get a small one every time I did a water change until I started using RO water. If you are using tap water, that could be the cause of it. I believe that a high level of silicates in the water is what causes diatom blooms. If its a new tank, a couple of diatom blooms is relatively normal. If all of your params are ok, it will usually go away by itself.
 
Or it can give you an excuse to get some sand sifters, like a goby or a fighting conch. The conch eats diatoms.
 
Here's a picture
pict0001tx0.jpg


I use water from the fish store--it tests zero for ammonia, nitrate, and nitrites. I have a Trigger so that limits me on sifters. The algae on the rock directly above the brown sand is actually deep red--not as it appears in the picture.
 
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I could be wrong here, but the way it's growing on the rocks looks like cyano to me. Have you tested for phosphates??? Even if they test low it could be that it is useing them as fast as they are made. But if they do test high it would be a better indicator that this is cyano. What type of flow do you have at the bottom of your tank??? If it is low I would increase that and the amount/frequency of water changes and see if that helps.
 
The picture is deceptive---what is on the rocks is a short fuzzy carpet red algae....surprisingly the lawnmower blenny loves it, but probably because there is no green algae anywhere. Flow is decent throughout, but probably lowest in this spot, which is the worst. I've got a phosphate test on the list...I'll take a water sample in tomorrow and see.
So I'll start there---thanks!
 
Ok--it's diatoms for sure. I changed 10-12 gallons on schedule this past Sat with RO/DI water as always. I used the siphon hose to suck up the brown stuff. Over the past few days it's back and covering the glass. Friday I added a powerhead which takes my turnover rate to about 18. I watch the air bubbles in the tank and they just swiftly, but not forcefully swirl around the whole tank at about the same speed everywhere. So I don't think I have any dead spots. Also--Sat I cut my light cycle down to 10 hours from 12.

Here's my parameters--verified by my LFS
Ph - 8.3
Amm - 0
Nitrate - the color is inbetween 5 and 10--I say 10 for my records
Nitrite - 0
Phosphate - 0
Alk - 3.75
Calcium - 320<--weird because Friday it was 420, Sat water change, Sun test shows 320. I'm at the bottom of my bag of salt (Instant Ocean)---possibly no calcium.

I've got yrs of experience with African Cichlids and I've never had a diatom outbreak happen so fast with Nitrates at 10.
Is this simply what can happen in marine tanks?
Is there anything else I can test for to shine some light on the situation?
 
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