Brown Algae Sandbed


New member
My tank has been running for over 9 months now, FOWLR 150 litres, the last few months I've been having trouble with what I guess is brown algae on my sandbed. I'm changing 25% of water each week hoovering the sandbed (which removes it all) then the next day as soon as I turn the lights on within a few hours it's back. Readings seem perfect Amm 0, Nitrite 0, Nitrate 0, pH 8.0, I'm using chemi pure elite, purigen, have a pellet reactor, i don't overfeed I just can't understand what I'm doing wrong - please help!


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Smoke Inator

New member
To me it does not look bad. Its never going to be as clean as day one. The easiest approach is to stir it from time to time. I wouldn't go more than 2 inches deep. I do mine every few days and it helps between cleanings and what the snails and crabs don't get

Fish Friend

New member
Good point, I have read many say that constant stirring is the way to go with sandbeds :)
Is it everywhere or in low flow zones?
And are you using RO water? tap water itself can contain tiny seedlings that can kick it as well.


New member
you can try getting tiger tail cucumber or maybe sand sifting star, but that all depends on what type of fish you keep in your fowlr. some will eat those 2 things


New member
I will never recommend anyone purposefully disturbing a sand bed in a marine system..
Let sand dwelling/stirring creatures take care of that on a smaller/less drastic level for you..

It looks like thats either diatoms or the start of some cyanobacteria.. You really didn't do anything wrong and thats fairly common in new tanks and can really happen at any time..
Diatoms usually feed off excess silicates which are very common with a new tank and can be reintroduced into an established system in many ways..

What I see there is certainly NOT a big deal and assuming it doesn't get much worse I wouldn't worry about it..

I will also state that I think you are "overfiltering" your system.. I see no reason that you need to run CPE/Purigen/Pellets other than I think you think you need to for a healthy system.. The fact you have that brown issue proves thats not true..

There is one more test that may show a reason besides a silicate test kit (not needed but would show if they could be a reason) and thats a phosphate test.. Do you have a phosphate test kit?