growth on decor and gravel

[Super8407]

I currently have a 75 gallon tank that is cycling. It is almost done and has no ammonia and now just has to finish converting the nitrites into nitrates. I kept on adding food until the ammonia reached 5ppm and then waited for nitrites to appear. Once they did I added in less food daily. My problem is that there is some kind of white growth on the gravel and on slates of rock. Some of it easily washes off. However, some of it seems to be embedded into the pieces of rock and will not come off. I did a fishless cycle and used fish food as a source of ammonia. Could this be some kind of bacterial growth or fungus or is it just from the fish food I added? The water is crystal clear and has no smell. I only added stress zyme, stress coat, and some salt. It is perfectly clean, other than the fish food that I added, some of which fell to the gravel. I want to make sure that this will not harm the fish that I plan on adding. The water currently has no ammonia, 2 ppm of nitrites and 20 ppm of nitrates.

 

[Zagz]

Welcome to AA. I would bet that you have food that is rotting in the tank as a result of the food addition for cycling. As long as there is no fish in there leave it be. Once you do your last water change before adding fish you can suck it out. You are getting close to the end of your cycle.

FWIW salt is not needed in FW aquariums. Depending on what you end up stocking with, there are many fish that will not tolerate aquarium salt at all well.