I am new to this forum and pools in general. First pool, Intex Ultra Frame AG 20'x48", approx 8000 gal. Older Kayak Sand filter (think it was made by Hayward) and 3/4hp pump. I had some trouble for the first 3 weeks clearing the pool with the crappy Intex pump that came with my pool, so I found a pump and filter on Craigs List and boy what a difference! Pool is sparkling clear. However, I have one concern that is still bugging me. I have these brown spots that keep coming back. They seem to come back to the same places in the pool (mostly wrinkles or seams but some just on bottom) each time. I can wipe/vac them away and in a few hours or the next day, they are back. Doesn't seem to get any worse (yet), but I want to know if this is just dirt or if it is some sort of stubborn algae that is trying to get a foothold. I have enclosed a pic but not sure if that will help. I have one of the good test kits on order but for now I'm dealing with the walmart 6 way kit. I ran out of CYA fluid, but I had put in enough conditioner to bring it to 30, so I assume for the moment that's where it is. PH is at 7.5 and clorine is running between 3-5. I have high alkalinity (300+) but it hasn't seemed to give me any problems considering how clear the pool is. and CH was around 120. Does this look like algae or just dirt? Do I need to shock the pool even though it is really clear? If so, I'll wait till my test kit gets here so I can really test it right. RIght now, I'm just enjoying my nice clear pool. You guys are great here and have already saved me a bunch of money on chemicals! Thanks for what you do.