JollyOtter, congrats on your new FX filter.
I use them and they are great.
How will your 75g be stocked ?
Dont under estimate the ability of foam/sponge media to provide
biological filtration in addition to mechanical filtration.
On my FX canisters, I remove the red baskets from the main trays. The top basket gets layers of foam/sponge. I place 30ppi foam sheet cut to fit in first, then the included round black Fluval foam pad in top.
I bought a sheet of 2" thick 30ppi foam
on Amazon from the "
Aquaneat" brand, and cut it to fit the round inner basket. The included black Fluval foam pad and the white outer sponge blocks are about 20ppi. PPI = pores per inch, where more pores per inch equates to a denser, thus more fine foam/sponge and less ppi is a more coarse material. Generally 10ppi is consodered coarse foam, 20ppi foams are medium, 30ppi is a medium-fine or fine foam. Most times 30ppi is the highest ppi used in filters.
The 30ppi foam pad I use catches a ton of muck and I haven't seen it restrict flow.
Also, I didn't place the included
Bio-Max in the baskets. I placed them instead at the bottom of the canister body around the outer edge between the outer wall and the inner lip the bottom basket sits on. Water enters the filter and travels down the tube to the bottom of the filter, where it exists and gets forced left/right then flows upward and into the outer foam blocks wrapped around the baskets.
With the Bio-Max spread out in that outer circular bottom channel, the smooth flow of incoming water gets broken up and the heavier and larger muck settles at the bottom instead of rising up and through the layers of outer foams.
When I clean the FX every couple of months, I find a ton of muck settled around the bottom circular channel the Bio-Max trapped.
Also, I took about 2/3 of the Bio-Max and broke them in half, then mixed them up with the unbroked ones before spreading them around the bottom.
I found the Bio-Max included on FX and x07 series canisters have a hard surface that doesnt seem too porous. Fluvals 500g bulk Bio-Max that's sold loose in a box is completely different. It has a very small inner hole (unlike the huge hole in the included Bio-Max) and the composition is very porous feeling. It's completely different and appears to be a sintered glass material, where the Bio-Max included in Fluval filters is a harder ceramic material. This is only a guess though.
How is the Polyfill working so far for you? I ask because I used it when originally setting up my
FX4 and don't use it anymore as a full layer.
I had tried using a layer of Polyfill, both the loose fill and batting styles, in the bottom basket on top of regular bio-media. I found with the high volume flow of water through the FX series filters, the Polyfill will end up catching too much muck and slow down the flow of water over time. So after the first time using it for a few months I removed it and never used it as a full layer
I do use the batting style Polyfill though as a "gasket" around the round foam pads in the inner basket.
I cut a length of the Polyfill batting the same height of each foam pad and wrap it around the circumference of the black Fluval foam pad and the 30ppi foam pad. It will act as a gasket between the edge of the pad and the inner wall of the basket. Water will still flow through it and will catch a lot of muck without slowing down flow of water through the filter. I dont use the batting behind the outer white blocks that wrap around the baskets.
You probably bought the loose fill version. You can use it also as a layer between the foam pads and inner wall of the basket.
**edit**
Here is a link to my album with old pics of when I set up my FX.
https://www.fishlore.com/aquariumfishforum/media/albums/fluval-fx4.7409/
One of the pics shows how I placed the Bio-Max at the bottom. You can also see where I had placed cycled Pond Matrix from another canister in the bottom center section of the canister body. I used a foam block from an
Aquaclear 70 and cut it to the shape I wanted to act as a dam between the Pond Matrix and the chute where water enters the pump assembly.
Ive ran it like that for 3 years and never had anything get sucked into the pump. That's a large void area that seems like a waste of space, so I figured out a way to utilize it.
Other pics show a pre-filter intake sponge in place of the intake strainer that I use.
approach.
