Depends on your bioload. How many fish do you have in there and how big are they? I took my HOB
filter off after I figured It was just too loud. Ammonia/Nitrite never spiked. After about a week, I put a Internal Filter in, Fluval 4+, after a few days, figured it was wayyyy too large (there goes 50 bucks). I took that out too. Both filters I had have two sponge and some carbon in it and I never went through a spike, if I did then it must have been a short one because I test every other day (doing hypo and want to make sure everything is goody goody). I think if you have enough LR
and don't have too much of a bioload then you should be able to take off the whole unit.