I was at my favorite lfs today and he said that velvet guard was the best thing for green water. Is this really the case? Please share your thoughts and experiences with this product.
I agree with Roan. Green water does not require nukes.
The best cure is to find the nutrient imbalance or nutrient spike that is feeding it, fix that, and water changes will clear it up. A UV filter will kill it off but if you do not correct the cause it will come right back.
Should I get a test for phosphates to see if that may be my problem?
I am using R/O water so my water should be stripped of most things initially. I have substrate gold under my gravel and I also put in the liquid form with some other plant fertilizer as well. I am thinking that with too much light is the culprit. I have done a few water changes and have had a few blackout days with no to little feedings for the fish and it is still the same.
What things should I test my water for in order to isolate the problem?
Green water is particularly fond of ammonia. Does your tap water have chloramine? The RO unit will not remove chloramine I think. Do some research, try the discus forums as they use a lot of RO and there is always some info available on search, SimplyDiscus and DAAH.
Meanwhile, just how much light do you have? More than 3wpg is a mistake IMO.