New fishtank! A few Cleaning/Stocking Q's

Its a 20gal..dont think its a high or a long more like boath of them put togeather...

And i got a feq Qs about em.

When i got the fishtank it had sand inside. Not the nice kind you see that they sell. But looks more like river/beach sand the greyish kind that has a varity of sizes of pebbles?

Do i have to worry about the sand being dirty and leaving back somthing that can kill the fish. I dumped on the sand out and wont be usein it.

Also you know one of them stick on thermometer? Well the it came with was put on crooked and was already half way pealed. So i just pealed it all off and it left some residue. How do i clean that off? Can i use anything since its on the outside of the tank and i will be rinseing it down with water after?

And what kind of fish can i keep in it?

I kind of want somthing nice and greenish kinda like a bass but not as large.
Also i want to take care of fry too and turn it into kind of a community breeder tank. Dont plany on keeping all the fry just a few so if other fish eats them its ok.

-Q

Well i am now filling up the tank in my bathtub to see if it can hold water.

Cleaned everything else and the sticker residue came off easly with just water.

Now i have another unexpected residue to worry about...It looks like a water stain but feels jellyish kinda like silicone. Pita to clean off! I even tryed to scratch it off with my finger nail but it wont come off..Will rubing alcohol work? I dont know if i have any in the house tho.

Other then that the tank looks great.

I think i saw some fish called Rainbows at my petsmart, looks like a minnow but the body is kinda whiteish with a green tail. But i read that Rainbows dont live long...

^yep just tryed that after i posted above. Works wonders...didnt even scratch my glass too.

Now theres a lil crack neer the top of the plastic border. Ima have to try to fix that...

^wow thats perfectly what i was looking for

Thanks