I was wanting to get this skimmer for my 125g. I also want to add an hob overflow box to this. If I add these two items, could I do away with my canister filter?
Im starting to get brown and red slime algae on the sand bed. I can`t seem to keep the sand clean I have a cleanup crew but they really do nothing for the tank. Should you leave the vaccume cleaning hose alone or should I vac.? I have vac. before but it will not siphon the algae. Should I redirect my airflow more to the sand floor?

Yes. If you get that skimmer you would be fine running JUST the skimmer. If your going to run a sump.....buy a octopus extreme. You will much happier with an in sump skimmer if you wanted to go with a sump under your tank.