I used the tea method with an aquatic, with some success, but I can't say if it is always reliable. I think the fungus could be destroyed (if it is fungus it is white) by growing the plant submerged for a week or so. This won't help with algae however. I find that algae is best discouraged by the use of pure loose peat as a medium, without sand. Sand always seems to support algae for some reason, and it should always be washed when used with utrics. Make sure if you use the peat that it is very loose and fluffy, not compact so the stolons can easily penetrate. I am leaning towards pure dead sphagnum as a medium, as the naturally low Ph discourages algae. Doadec's method is good if the problem arises: spraying removes the micronutrients that support the algae, and eventually a balance is reached where the algae no longer proliferates. With aquatic species, it is
more difficult, and I have found that usually the only thing to do is to make a new aquarium with clean water, transplant the utric, and then keep the whole in lower light. Man, I hate algae!