Ive had multiple dirted tanks for a while now and have never had this issue. There is a green mold like substance growing all across the dirt in my 180gal and now there is a white substance as well. Has anyone had this issue before? What is it, is it harmful, and how do I get rid of it? Thanks guys.
that bluish green slime is blue green algae, cyanobacteria. once it takes a foot hold your tank is going to crash hard unless you use an antibiotic on it. the white is indeed mold. its just breaking down organic material in your dirt.
get yourself some h2o2 and a syringe. inject h2o2, hydrogen peroxide, directly into the substrate as deep as you can go SLOWLY!!! this will help but not cure the problem. the cause of this cyanobacteria is excess nutrients. since you're dirting its almost impossible to get rid of excess nutrients.
should go with a commercial plant substrate next time
I also had this in my last planted tank set-up and I do not believe that it is cyanobacteria, but the live bacteria in the dirt. As my tank became more and more mature this bluish green substance showed up more and more, but only in the dirt. It never spread to my plants over the year and a half that my tank was set-up. Since then I have torn down that tank and have since set it up in a different tank using a different technique of completely covering the dirt in the front and on the sides so you cannot see the dirt at all. I have yet to see this show up again.
Good luck with your tank.