I have what looks like red algae taking over my tank. I scrub it off treat water with algae killer and two weeks later it's back on my decorations and walls of my tank. Any ideas?

If it's by a window keep it away

You can call them. they are very knowledgeable about that stuff.

A powerhead or wavemaker will help increase water movement. Perform regular water changes and routinely replace mechanical filter media. Maintain proper marine pH between 8.1 and 8.4 with buffers or with kalkwasser. A high pH helps discourage aggressive growth of RedSlime Algae.

I would go down to Bakersfield aquatic pets and talk to Steve about it he is very helpful and knowledgeable about all kinds of things