Fluval Spec V MBBR Filter Setup

I converted the filter on my Spec V tank to a MBBR (Moving Bed Biological Reactor) with a mechanical prefilter.
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updated April 11, 2024

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I got a Spec V tank for my office. The filter media it comes with is okay, but I don't like buying a lot of replacement media and fiddling with my tank a lot. So my setup is a planted tank ecosystem, with zooplankton (copepods, daphnia, worms, etc), shrimp, snails, and small fish. 

To better facilitate a hands-off setup I need good bio filtering to keep ammonia converting into nitrogen for the plants, and keep the tank gasses balanced for plant growth and fish health. So I decided to build a MBBR using the filter space on the back of the tank. 

This setup (from bottom to top) has an air stone in the bottom for aeration and flow (air line comes in from the pump side), a fistful or two (about a cup) of k1 media, a filter basket to hold some bio balls or filter floss, and above that there's a sloped divider that slides in. The divider keeps a portion of the original foam filter in place to act as mechanical filtration, while directing the air up a vent at the back, creating a quiet gurgle. 

Everything is setup so that shrimp would have a hard time getting through.

 

Printing: 

Filter basket: 4 walls, 0 top and bottom layers. Pick your infill and go. I used 20% hex, oriented 0°.

Spacer: 2 walls, 0 top and bottom layers. Use aligned line infill, oriented 90°. I used 30%. mind the long bridge near the end of the print.

Guard: lay the largest surface on the bed, pick infill and print with  0 top or bottom layers, 2 or more perimeters.

 

Assembly: 

put whatever media you want in the bottom (I used some Eheim bio balls) and then push the spacer in, being careful to push it down evenly. I cut the bottom section of the original filter sponge to fit on top, laying flat against the spacer so it's angled to the front opening.

Once the basket assembly is put together, it just slides in and hangs in place. The corner bumper will kind of lock it in, so you will need something to pull on the back corner to pull this back out, but you shouldn't need to do it like, hardly ever once the MBBR is running.

When fiddling with the pump I had a few K1 nuggets pop out, so I have added a little guard that you drop in to cover the hole that leads to the pump. I snipped some segments off the back corner to allow room for the air hose.  I also have the sloped section facing the pump so it will push it out of the way during installation. See pic.

 

Video of the MBBR running:

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