Tank issues..

[kien]

Without a skimmer you will want to find an alternate way to oxygenate your water. Either use an air stone with a pump or point some powerheads at the water surface to agitate it more. Lots of people run tanks without skimmers and this is fine so long as you do frequent water changes and keep your water well oxygenated as described.

[Magma]

good to know, I always keep my powerheads pointed toward the surface so i get a good wave effect on the water. Just keep testing the water and doing changes i guess...

[paddyob]

+1 on being ok without a skimmer. You only have 3 fish in a 40 gallon tank so your bio load should be relatively low.

Just ensure to watch your feedings and other controllable factors.