Algae Problem... Please help!

[BlackMollyJenny]

My tank is about a year old and I've had this problem earlier but didn't really do anything to prevent it. I've got algae everywhere, my sand, (fake) plants, rocks, caves... It just won't go away.
I've tried scrubbing it with those dish scrubbers but the plants just end up falling apart, and I'm too afraid to use any kinds of soap or bleach.
The kinds algae I'm seeing is carpetish brown algae that grows on my decor, and darker coloured algae that grows under the surface of my sand. There is also weird lighter coloured sand that also grows under the sand.

I'm not sure if it matters but, the fish I have are a dojo loach, a red finned/rainbow shark, a black molly, and about 11 guppies (some are babies and I am trying to get rid of them).
My tank is a 20 gallon Aqueon tank with the same brand filter and heater.
My fish seem healthy and aren't suspiciously dieing, actually, I haven't had a death in a few months.
My decor includes 7 different fake plants, two (previously) white caves, a black rock, and a piece of driftwood.

Anything helps, thank you!

(I did make a thread about this a while ago, but I tried the advice given and it didn't help)

 

[Brookster123]

How long the lights on? Wc routine?

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[BlackMollyJenny]

I leave the lights on from usually about 10 to 6

I clean the tank every three weeks

 

[Brookster123]

You change water every 3 weeks? How much?

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[BlackMollyJenny]

Usually about 20-40%, but every other change I do 50%

 

[Mebbid]

Usually about 20-40%, but every other change I do 50%

I would say that's one of the main reasons then. Try kicking that up to 50% weekly and leave your lights on for only a few hours a day until it clears up.

The decor can be safely bleached to kill the algae. Just rinse and let dry. Bleach inactivates rather quickly when exposed to the environment.

What are your nitrates at?

 

[BlackMollyJenny]

I would say that's one of the main reasons then. Try kicking that up to 50% weekly and leave your lights on for only a few hours a day until it clears up.

The decor can be safely bleached to kill the algae. Just rinse and let dry. Bleach inactivates rather quickly when exposed to the environment.

What are your nitrates at?

I'll try that, I'll have to get back to you a little later. I don't have a testing kit but I'm planning to drop by a pet store today or tomorrow.

Also, would getting a live plant or getting rid of the drift wood do anything?