Uv Light & Fertilizer

At least some can. A level one UVS can rip apart the chelated bond if the traces are chelated. Iron is a good example. If the iron is an EDTA or DPTA form, a level one UVS will destroy the bond in about an hour and the iron will become unavailable to the plants in the short term. The fertilizer itself is not affected. So, macros are fine. I do not know if the cheaper, lower exposure, UVS's that are used only for green water are as destructive to chelated bonds.

Because of this, I use a gluconated iron, such as Flourish Iron. Many of us mix our own micros and these salts are not chelated. I think that @burr740, a member here, sells this in a package if you think you need unchealted traces. Many of the branded products are also unchelated, but you would have to look into that.