# Diatom outbreak?



## Superfly724 (Sep 16, 2007)

I've had the tank itself set up for about a month and a week, but just added fish about a week ago. This is a 90 gallon tank with only 3 small juvenile fish in it as of right now. The substrate is Pool Filter Silica Sand, which I assume is the problem. Basically, my sand is turning a nasty brown. I'm assuming it's some sort of bacterial or algae outbreak, but I'd like your opinions to verify, and help me get rid of it and ensure the safety of my fish. Attached are 2 pictures. One of them is of the sand as it normally looks, and the other is of the brown patches.

Note: I'm assuming this is from the silica as well, but there's been a sort of film at the surface of the water. A few days after I added the fish it started to break down and now there's a bunch of holes in the film. Not sure what this is. Water changes don't seem to have done anything.

I would give you my water parameters, but I added some Prime so they all read clear. Ph is around 8.2, and the water is rather hard.


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## Osiris (Jan 18, 2005)

Yes, Silica sand is the corporate here, feeding the diatom algae. Hate to say it but if want it gone get real sand................


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## emc7 (Jul 23, 2005)

diatoms are right on time for that age tank. Sometimes they will go away after some weeks. Sometimes it will be replaced by a green algae. IME, low-light, silica, and hard water all favor the brown stuff. Its not harmful to fish and a few will even eat it if there's nothing else. So don't panic. I'd wait and see what happens. If you do kill it, be sure to scrape and siphon all the dead stuff as it will rot. Though that may not be too bad in a large tank with a low bioload. 

Think about adding more light. Maybe a 2 bulb fluorescent or a T-5 instead of the typical one T-8. If you can get it to grow green, you can find a fish to eat it.

Everyone says sand is the best and most realistic substrate for lake cichlids but it does have some drawbacks. One is the way it shows everything. See if you can siphon the spot off the sand without sand coming out. If you can't stank looking at it, you are in for a lot of maintenance. If you can, the fish won't mind. 

IME a floating film is either oils (from food or water conditioner) or fine dust (substrate or buffers) or both. It can be broken up by agitation and caught by fresh carbon in the filter or you can skim it off or soak it in a floating paper towel and throw it away. A film is usually not harmful, but it can reduce the oxygen getting into the water and its ugly. If it goes away on its own, down worry about it. If it persists, attack it and see if it comes back.


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## Superfly724 (Sep 16, 2007)

Dang... I knew I should have gone with the 10,000k bulbs. I'm currently using 2 6,700k bulbs that I purchased because the 10,000k bulbs were more expensive. I had a feeling I should have spent the extra money. I do have a light fixture that can hold a total of 4 bulbs, though only 3 of the sockets work since some of the pins corroded in one of them. Should I turn the 3rd bulb on to add light? 

I'll try and see what the siphon does. It's time for a water change anyways. Thanks for the help!

Guess I may need to stray from the complete biotope and get a Bristlenose or two.


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## emc7 (Jul 23, 2005)

You could get something like a featherfin that moves sand around. Really, wait a month and see what happens. What you have now may not be what you have in a few weeks.


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## Superfly724 (Sep 16, 2007)

emc7 said:


> You could get something like a featherfin that moves sand around.


Will he not attack my shellies since they are also bottom dwellers? I've actually got a Eupterus left over from my 55 that I've been trying to get rid of for a while. I've been considering adding him, but that would mean I get absolutely no fry, and since the shellies are also territorial and bottom dwellers there may be some trouble.


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## emc7 (Jul 23, 2005)

true. There was a 90 gallon display tank at ACA with 2 furcifer that dug two pits and drove off the other fish.


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## PuterChickFL (Feb 23, 2010)

i have a 56G tall tank that had a huge outbreak recently. my substrate is not sand it's gravel, and it's been established about 6 months


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## Superfly724 (Sep 16, 2007)

That's rough. It's really unsightly stuff, but I guess I'll just stick it out. If it were a rock or 2 that were covered I would be fine. I'd just take them out and scrub them, but sand is just such a hassle to remove and replace. Lesson learned, though. I get what I pay for. I spent less than $20 on enough sand for all of my aquariums. Next time I'll just suck it up and go with Aragonite.


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## Superfly724 (Sep 16, 2007)

Update: I've had the lights off for pretty much the whole day every day, except for feeding times. It appears to be growing lighter on the sand, and the brown on the rocks has kind of turned almost grey, and looks like it's maybe rotting. No nitrates visible in the tank yet, but I did lose another fish. He had been hiding in the rocks for the past few days and I found him stuck to the filter last night. 

I'm assuming it will come back if I turn the lights on for extended periods again. Not quite sure what to do, now. Hopefully I can get it to be gone completely and control it.


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## toddnbecka (Jun 30, 2006)

Diatoms don't need light to grow, and they're completely harmless aside from appearance. They usually turn up about a month after a new tank is established. A bristlenose pleco would be the easiest solution, but you'd need to supplement its diet at least until the algae does get a decent start.


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## ddawgs3 (May 13, 2010)

Crayfish maybe if you put your fish in another tank for a while?!


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## Superfly724 (Sep 16, 2007)

toddnbecka said:


> and they're completely harmless aside from appearance.


Couldn't the decomposition cause a spike in Ammonia or Nitrites? At the time of death there were 2 fish in the tank. Both were only about 1 1/2 inches long, so the bioload would have been minimal.

I would use a Pleco, but I'm really reluctant since I was trying to create a biotope. I'll only add one as a last resort.

After checking again this afternoon, it's almost all gone from the rocks. Is it possible they've consumed all the Silicates in the tank and won't return?


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## emc7 (Jul 23, 2005)

Lol, sand is mostly silicates, so if you have sand left, you still have silicates in the tank. I suppose they could have eaten all of one thing thing they need from the water, maybe the dissolved silicates, maybe the nitrate. I'd guess fewer silicates would go into solution once you add "cichlid salts", but I never count on any slime being gone for good. 

Yes, killing them all at once would make an ammonia spike just like dumping in a lot of extra flake. 

What tends to keep the brown algae under control is something else growing faster, such as a green algae. Whether thats an improvement depends on your point of view.


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