How much live rock do you have and how long have you had it in the tank ?
Substrate as well.
Adding a skimmer may be a good idea, but don't ever remove an existing installed power filter and replace it with anything, in this case a skimmer.
Keep running the filter AND add the skimmer. Run them both at the same time for a period of time. See if the skimmer is doing anything, and if your water quality improves.
Then ...
Depending on the quality/quantity of rock and sand, and maturity of your tank, number of fish/inverts you have ... and your water test results ... you may be able to eventually remove the Aquaclear.
Prizm or BakPak2 would be fine for hang on skimmers, unless you have a sump or want to hard pipe an external skimmer. Your choice
HTH