well yea, but taking all your substrate out, and adding sand, will cause your tank to recycle.
also,
like i said, i have no idea on the pool sand, never see/heard/read about it.
id go for the playsand. Grins has a habit of hitting the nail right on the head.
i mean heres the gig dude, you're just starting out. youre overwhelmed with info and stressed cause you stuck between brackish and salt.
youre also stuck with a mono, GSP, and a damnsel. so lets talk about yer fish.
the MONO.
if you keep your tank brackish, he'll have to o in like 4-5 months when he outgrow a 20 gal. (NOTE i had monos in a 75 gallon tank. they were FRY when i got them like the size of a quarter. 6 months later puffer punk was up my *** because they were WAAAAAY too big for my 75gallon. you have a 20)
if you go salt, the monos gotta go now. period. cant be in there for the cycle, cant be in full marine for another year (well, shouldnt)
Yer. GSP
i have no idea. never had no intrest/therefore retained no useful knowledge.
The damsel. if you stay brackish, please take him back. and if you go salt, he SHOULDnt be in there for the cycle
adding liverock will also cause you tank to cycle. depending on the LR, it could be a full blown cycle, or a lil mini one.