Filter intake tube positions

PicturePrefiltered intake on 55g Mbuna tank. Photo by the author.

How deep do you have the intake(s) of your filter(s)? Where you position the bottom of the intake can matter in several different ways. In fact, you don’t even have to position the intake vertically, but that’s a story for another day.

If you have sand substrates and you seem to regularly get sand in your filter, you should consider raising the intake. A little sand in your filter isn’t going to destroy it. It may decrease its lifespan as it wears on the impeller, but that’s unlikely to happen quickly unless the intake is gulping large quantities. How much sand gets in your filter might also correlate with the cichlid species that you keep. Larger species kick up greater volumes of sand more often. You can mitigate some of this by prefiltering the intake with a sponge, but be cognizant of the sponge’s PPI (pores pre inch) density. Too dense and it will collapse from the water intake pressure. Too sparse and too many particles (including sand grains) will get through. I use approximately 30 PPI sponges on my intakes. Some folks refuse to use prefilters because they claim the sponges place too much pressure on the filter impellers. I disagree.

I don’t unplug my filters when I do water changes, even though I change 50% of the water each time. My intakes are deep, so I don’t have to worry about the water dropping below the intake. If you have a filter that isn’t self priming and you want to do large water changes, I would suggest that you make your intakes deep also. Otherwise, if you do a very large water change and the water line drops below the intake, you’ll have to manually prime your filter to get it restarted. I’ve posted an easy trick for priming problems. The other advantage to having a lower intake is that it will better capture any detritus that gets stirred up by the fish.

It might take some trial and error to find the intake sweet spot, but you’ll find it. Experiment and see what works best for you. You don’t have to prefilter, but I do and I highly recommend it, especially if you have live plants. Plants shed lots of bits and pieces, which are easily caught by the prefilter, turning the intake into an extra mechanical filter, ultimately decreasing the time between filter cleanings.

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