Algae is an annoying green entity that you will find where ever a nutrient rich water solution and light mix, that is just a fact of life. It grows on the tops of aero tables or on rockwool, pretty much anywhere that light hits. Although this is not going to harm your plants it will eat a bit of the nutrient solution and look unsightly.
There are a few tips to help slow it down, one is to use a “ZYM” in your nutrient solution the “ZYM” digests the algae and keeps its numbers down. the second is to cover the surface of the affected area so as the light cannot come into contact with the nutrient solution.
Out of the two methods I would recommend the use of “ZYM“, as it gives you a two fold effect not only will it keep the salt build up and algae down it also helps to keep your roots looking white by digesting dead root matter before it has a chance to build up and cause damage. Keeping the nutrient solution temperature down can also help reduce algae and would do well used in conjunction with a “ZYM“