Brown algae

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Aquarium Advice Regular
May 12, 2021
illinois USA
I have a 20 gallon established tank and over the past month I have been getting alot of brown alge building up on the decorations in the tank I don't have any live plants in it. It has a few fake plants driftwood rocks and a artificial rock structure. Inhabitants are guppys neon tetras a blue dwarf gourami and a golden mystery/apple snail. Light is on for 8 to 10 hours a day usually. Any advice on how to get rid of the alge from my decorations or atleast control it would be helpful. to me it makes the tank look bad.
Is it possible your water parameters might be off without you noticing?

How long has the the tank been running? Diatoms usually clear up on their own after a couple of months of being cycled.

With no plants in the tank there is nothing to compete with diatoms/brown algae for nutrients.

I dont think mystery snails will eat diatoms, so maybe try 1 or 2 nerite snails if you wanted to go down the route of having something eat it.

Turning up the light can help promote green algae which will outcompete the diatoms for nutrients and are typically easier to deal with. 8 to 10 hours light seems a lot though, so maybe cutting it down will kill of the diatoms. Maybe your lighting is at a sweet spot for diatoms.

Its fairly easy to manually clean off diatoms manually.
brown algae is known as diatom; it is fairly common in a new aquarium as it feeds off silicate. While it is annoying; if you are patience; it typically disappears after 2 or 3 months and never comes back.
I would rather have diatom than green algae since it will vanish over time but green algae is the gift that keeps on giving.
The tank is cycled and has been going for about 6 months its not a well seasoned tank but its not new either
Its been about 2 weeks since I checked my water parameters but last time I checked everything was good ammonia was 0 nitrate was 0 and nitrite was low I don't remember the exact number but it was well withing safe levels. My local water supply is high ph about 8 to 8.2 and it's hard water
I see. I never setup an aquarium without live plants. I presume you do regular water changes. I think Aiken Drum answer was better than mine in that you have excess nutrients in the water and the brown algae is eating it. Some fishes (sae for example) will eat diatom (sae are way too big for your aquarium); and live plants will help eat that extra nutrient. I'm not a fan of green algae. Water changes will also help to remove extra nutrients. Fish waste is some of the nutrients being added to the water.

While water changes are good for the fishes; you do have to be careful else you can kill the fishes. The new water needs all chlorine removed and should be near the same temp. as the tank water.
While whatever is feeding the brown algae is in the tank you wont be able to deal with it other than manual cleaning. As said it tends to clear up over time as either the nutrients are taken up by something else or they simply run out.

Silicates are one of the main things brown algae feed on, and one of the sources of silicates will be new substrate. Over time the silicates will leech out of the substrate and get used up. This is why brown algae often disappears on its own given time.

Over time, especially with your lighting period and no plants, green algae will develop and out compete the brown algae for nutrients. While lighting isnt as important for brown algae growth as it is for green algae, you could go the other way, and try and starve the brown algae of light. You might not like looking at a darkened tank though, so maybe isnt a good route for you.

Upping the water change frequency can remove nutrients from the water, depends on your tap water. You could be adding nutrients. Some tap water is high in nitrates and silicates for instance.

Try adding some live plants to take up nutrients. Java fern and anubias are really easy to keep. Just attach it to a rock, piece of driftwood or plant weight and drop it into the tank. They are very low maintenance, dont need strong lighting, dont need substrate at all, but may benefit from weekly liquid fertiliser.
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