Moss all over pool bottom under liner - patch over?

[skittles]

Hi! I'm new to the forum and have only a year of pool ownership. We bought our home a year ago, and although the seller said "new liner", it had holes in it due to them throwing powdered shock on the pool floor and burning it - plus it was a very cheap, thin liner. (The owners died and the daughter just wanted to get the place sold and took shortcuts big time. We bought the place as-is but couldn't see the liner through the cloudy water.)

We have a company replacing it, but when they took up the liner the bottom (vermiculite) is all pitted (large indents) and about half is covered in mold and moss. We sprayed everything with bleach water and let the sun dry everything. Today I went about scraping the moss and mold up with a spackle knife. I also went around and wire brushed a lot of the less damaged areas. My husband said I probably don't need to get it all up because we are skim coating all of the affected areas with a sand mix (Portland cement and sand - can't find vermiculite). He says the concrete will kill everything and it should be okay. We are not super skilled in this. We're trying to save some money by DIY. I am pretty good at finishing concrete though - which is funny. I'm a hobbyist-artist so that's probably why.

So, my question is, do I have to get every little bit of mold up? Will the concrete pretty much take care of it? I'm only talking about dried up flat spots. Thanks!

[PoolDoc]

Stuff growing under a liner is occasionally a problem, usually in the form of dark stains that can't be removed because they come from underneath. But, I've never known of such stains being more than a cosmetic problem.

I don't know that putting new sand mix down will kill anything, and the effect from bleach is likely to be temporary. If you want to experiment, you could make up a copper sulfate + borax mixture and spray with that: it would be longer lasting. You'd probably want to start with a strong water and copper sulfate mixture, and add borax till you get a neutral pH . . . and then spray that.

BUT, that would be an experiment -- I've never done it -- and there might be some weird reaction from it that would damage the liner. So, no guarantees. But such a mixture would probably be a pretty strong fungus & algae inhibitor.