My first adventure as a grower

Yeah algea would be green, caused by light. Brown could either be nutrient stain or bacteria, I have used the tri products before and they are fine for dwc, not sure on some of the other nutes. I found hydroguard a good product to keep the res cleaner then when u used other rooting products. I'm no expert on dwc, I have only done about 7 grows in it.

Greenish would be algea, meaning there is light getting inside your reservoir. The brown stuff would be something bacterial. Make sure no light gets inside, use H2o2 as I mentioned in your other question you will need to play with the dosage and put it regularly into your nutrient solution. Beneficials are also a way to go but just dont use them in the same nutrient mix with h2o2, good beneficials are expensive, you don't want to waste them. I recommend the dry beneficials btw, liquid just turns bad to quickly for its price. In hydro you need to work really clean if you decide to go steril, this means everything, the reservoir all airtones and tubes and other cables need to be cleaned on a regular basis, if nothing works out, there is still UV filters that may help you if you have uncontrollable pathogen pressure in your water

some h2o2 would probably be effective, you have to look up the dosage yourself though or wait for a hydro expert to reply