If it is terribly gross, I would recommend doing a complete water change. Even though it will probably stress him out, if the tank is that covered in algae, it will help the appearance of your tank and your fish's health. Make sure to rince the plants and gravel thoroughly with hot water. Changing the filter media will definetely help!

 

Won't that kill my cycle? It's a cycled 10-gallon.

And won't hot water be bad for the plants? They are live plants.

I'll definitely change the filter media, then.

 

No, do not do a complete water change. Yes, hot water would be bad for live plants lol. Also, definitely do not change the filter media as that is where most of the tank's BB lives.

I would just begin by treating conservatively. Decrease your photoperiod to 4hrs/day, continue to do this until the algae is gone or until your plants begin showing some wear from not enough light.
Personally, I only leave the lights on in my planted tanks for 8hrs/day, but once you get the algae under control you can play around with the times and see what works best for you.
If you find that you still have algae issues, a photoperiod that seems to keep algae at bay is to leave the lights on for 4hrs twice per day with a 4 hr break in between.

 

I just did a 3-gal water change (tank is 10) and brushed and rubbed off as much algae as I could. I'll be gone for the weekend, so the lights will be off from tonight until Sunday night. I'll start leaving the lights on for only four hours when I get back.

Are you sure I shouldn't change the media? It's pretty gross looking, it's covered in furry algae. I guess that's where the BB are, though, right?

 

You can rinse it off in the bucket of dirty tank water next time you do a water change, but do not worry about it too much. You kill the BB, you kill the cycle, and most of the BB is in the filter media. In most cases it is actually perfectly fine to do a large percentage water change on an established tank if necessary because very little BB actually lives in the water column, it is all on the filter, walls, and decorations.

 

This algae usually appears when CO2 and nutrient levels are very low, and light is excessive. Remove as much as possible using a toothbrush and a narrow siphon hose. Then increase CO2 and nutrient levels.

Water changes won't do much tbh, if anything it'll make it worst because you're removing more nutrients from the water.

 

How do I increase CO2 and nutrients?

I have root tabs in the tank for my amazon swords, aren't those nutrients? If so, I guess it's not enough.

 

You can purchase Seachem Flourish comprehensive, which will take care of the nutrient side of the problem. CO2 supplementation can be achieved by Seachem Flourish excel, but I have never used it and can't comment much further. However, I wouldn't go out and spend a bunch of money just yet. If you continue to have algae problems then I would consider investing in these things

 

Manually removing algae works best for the non-persistent algae, blue green algae and black beard algae usually require more drastic measure like hydrogen peroxide/Excel spot treatment.

Hair algae is easy to remove, just take a clean toothbrush and swirl it around, you should grab the majority of it.

Also the CO2 & nutrient thing is just to prevent the algae from coming back, limiting your photoperiod would also help but manually removing algae always seem to work best for me IME. It's how I got rid of my BBA.