Hi JRPW,
Oh Brother I feel your pain, trust me I really do. That brown algae (diatomous algae)on your Eleocharis hairgrass is a real pain to get rid of. I've tried brushing it off, siphoning it out, trimmimg, and the next day it is back just as bad as ever. See my thread about 'Is UV any good for removing algae. Everything recommended is in there. Trouble is I don't think there is just one magic solution for curing this plague. You have to hit it from all angles and hope you strike lucky that something you do or a combination of all of them will beat it. I have tried almost everything so far and today I finally bit the bullet and decided that the Eleocharis had to go, I pulled almost a bucket full out of the tank today.
I can see you have got the brown brush algae as well which doesn't look good, so something is definitely wrong with your maintenance regime, and the water parameters. You are going to have to be pretty ruthless and cut everything you can see that has got algae on it, nothing you put in the tank will reverse or remove that amount of algae. If you have got 120 litres of water in your tank and only changing 24 litres per week, which is roughly a fifth of the volume, you need to try doing 50% twice a week. Add Seachem Flourish Excel or Easy Carbo to boost your Co2. If you drain 50% of your tank out and the plants are exposed, use a week or diluted solution of Flourish Excel in a spray bottle and spray the leaves with it, or paint it on with a brush. WARNING Be very careful when doing this, if you get the mixture too strong you will completely nuke your plants altogether.
Better to try a weaker solution first, you can always increase it gradually if you are not seeing results. Cut both lights for 5 days and try the Black out, completely cover the tank in black bin bags and starve the algae of light. When you put the light back on only use one of them for a shorter period, maybe two or three hours in the evening. If the tank is exposed to sunlight or bright day light from any side of the tank, keep that side covered during the day. Anything that you can remove that can be scrubbed like wood or rocks get them out and boil them or even try scrubbing them with a weak bleach solution, then leave them soaking in fresh water for 24 hours before putting them back in.
If you are injecting Co2 ramp it up as far as you dare without killing your fish. Turn the temperature up to about 29 degrees for two days you may have to put an air stone in there also if the fish are gasping at the top. Talking of fish, how many have you got in the tank, one of the things that I am sure triggered this in my tank was an increase in the bio mass from the fish and the increased feeding. Even though I had great flow around the tank the eleocharis just seemed to trap all the gunk flowing round the tank.
If you see the pictures in my thread the brown algae was as bad as yours.
The good news is that with the determination of an 'Algae Warrior' and keeping at it you will turn this around.
Good luck and keep us posted.
Cheers,
Steve.