OK here are more details:
20gl tank kept at 80 degrees
I am using strictly RO water since this started but before that I used half tap and half RO(the tap I let sit a day or 2 before change)I change this
once a week and do about 50%.
I have pressurized co2 going at 25ppm give or take a few
currently Nitrate test reads zero ppm
kh tests at 6 and ph is at 6.8 which verifies my co2 is correct at 28ppm
I have no phosphate test at this time so no info on that and it's my biggest suspicion since everything else seems to check out.
I never dose this by the way.
My lighting is a single 65w pc
which I run 10 hours a day
My substrate is Onyx sand
My plants are wisteria,rotala indica,java fern,baby tears(i think)
and some plant I don't know the name of that grows out of control.
also I have a pretty good carpet of hair grass going.All the plants were doing fine before and still are inspite of the light being blocked out by the algae cloud.
My fish are 2 female guppies,3 Panda cory's,2 otto's,4-5 Japonica shrimp,
1 grass shrimp,1 female Ram and 1 male Ram.I feed 2 times a day and it's always devoured so I doubt this is adding phosphate to my water but
since I can't test I don't know for sure.
As far as dosing goes I go real easy on that.I do not add kno3 because under normal conditions it almost always reads between 5-10 ppm.According to what I've read here thats right where I want it.Every now and then I need to add some and I use stump remover.I use Chuck's calculator to figure the amount.
I dose k2s04 once a week and I use Chuck's calculater to figure out how much to add.From memory I think it's something like .25 of a 1/4 teaspoon I need to add.I think I read that it's hard to overdose this stuff anyway and I'm pretty sure I'm not.
The things I have done to fight this algae bloom are as follows:
My 1st attempt to deal with this was to let it play out.I let it go for about 2 weeks thinking it would burn itself out and use up all the nutrients.I finally couldn't take it anymore and went with the following plan.
1.I did an 80% RO water change
2.I turned off the lights for 5 days straight.My tank is in an enclosed cabinet that has walls and doors so it was completely dark during those 5 days.
3.I did another 80% water change at the end of the 5 days and turned the lights on
4.1 day after the lights coming back on I did 1 final 80% water change
It's been 2 full days since that last water change and already the water is turning green.It's like super algae or something.
Well that covers everything I could think of that might be useful.I apreciate any help.