If tank is running without a filter (any water movement?), I’d recommend virtually 100% daily water changes with cooler water (16-20*C)
(maintain tank at cooler temperature for plants)
An Eheim 350 Skim would do a decent job of keeping the surface clear and moving CO2 through the tank (except for possible hardscape limitations on circular flow)
In a 45P (& 60P) the usual sort of intank diffuser (Tropica, Aquario etc) is usually sufficient for CO2 delivery - one advantage of the diffuser (esp Tropica) is that you can glance and confirm bps and fine CO2 bubbles