Diatoms?
 

My tank has been up for 6 months and I've tried reducing light, increasing light and I can not get rid of this algae. I think it's diatoms but it doesn't come off of the leaves easily like I've heard. I'm not really sure what this is and any help would be greatly appreciated.

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looks like diatoms or brown algae to me.

Best fix... Otos hands down. Also if your bulbs are old then that may also be the issue. in the words of Tom Barr. "if you grow the plants, you wont have an algae problem"

I try to follow this. If i focus on growing the plants, ie providing enough co2, ferts, proper light cycle, then algae will disappear

Will doing a blackout help with this?

A blackout won't help, this kind of algae thrives in lower light.

How long are your lights on for currently. How old are the bulbs? Are you dosing ferts? Co2? Any algae eating fauna currently? RO/DI or tap for water changes?

Lights are on for 7 hours, bulbs are 6 months old, no CO2, osmocote plus root tabs, 2 ottos and 1 Siamese algae eater, tap water, standard 75 gallon using two 48" T5HO bulbs 8 inches above the surface.

hmmm.. I truly think this is a no co2 issue. Try dosing with excel if you dont want to dive into the world of CO2, but I can tell you from experience, CO2 is the best algae control

I've got the same problem. What is excel.

excel is glutaraldehyde... Think of it as CO2 in liquid form.... but nothing beats a full co2 system

I have paintball CO2, I just got tired of having to refill every two weeks. I bought an electronic solenoid to be able to turn it off at night but i didnt realize that i had to have a way to regulate the 800psi from the tank, down to whatever the solenoid requires.

For diatoms, you can make use of Siamese algae eater and RO water change.
Another fact that you must take into account is the presence of GSA (Green sport algae) that emerges in low phosphate condition. you can add some K2Po4 (potassium phosphate)

I'm glad I found this thread, because I just started having the same problem. My lights are 2x24 watter T5s, on for 12 hours a day, the bulbs are about 8 months old, I dose a capful of Excel every 3 days, and no algae-eating fauna. I use tap water for water changes. I did a 20% change today. What should I do?