'T' Connector Options(?) and Customizing a Pre-Filter Design?

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Aquarium Advice Apprentice
Jul 28, 2017
I just set up a new canister filter (Oase Biomaster 600) in my 37 gl. turtle tank. This filter has a unique feature: an easily removable for internal pre-filter comprised of a stack of 6 cylindrical sponges totaling approx. 12'-14" tall. The stock pre-filters that came with mine are 60ppi charcoal filters and Oase also offers 45ppi and 30ppi replacements. In setting up my filter I used my own 20ppi cylindrical foam for the pre-filter.

I've always used an in-tank pre-filter over the intake tube's strainer for the purpose of keeping the strainer unobstructed (lettuce, food waste, etc.) due to the larger surface area of the sponge. I think this pre-filter foam is around 30ppi (the only cylindrical sponge of the size I need that I could source). I clean and change this pre-filter about once a week (or longer if lazy when it starts clogging slightly).

While researching canister filters, I cam upon an Eheim pre-filter product which is essentially a cylinder of foam inside a case. It's the sort of a reverse of my own pre-filter system insofar as the strainer is on the outside and the foam on the inside. I tend to think my system is better(?) for preventing pre-filter clogs in a messy turtle tank with large chunks of debris, decaying lettuce, vegetable matter, and waste. One small downside to my old pre-filter setup is that occasionally the turtle would pull off the pre-filter sponge (the sponges internal hole size could benefit from being a little smaller for a super tight fit, but I could never find one with those dimensions) or even occasionally the sponge along with the intake tube's strainer. I think the Oase Biomaster filter I now have has a more secure intake tube design (my previous XP3 used many sectional pieces of tubing that stacked together and could be separated by a stone turtle). One potential(?) benefit of the Eheim design is their pre-filter cage - although potentially more easily clogged with vegetable matter - may prevent dislodging of the sponge by the turtle. On a downside people can't seem to source replacement sponges from Eheim and the sponge is too fine for my needs anyway at 30ppi+/-.

However in researching I found an image from Eheim that I found intriguing: dual pre-filters connected by a 'T' (see central image in attached pic).

New Pre-Filter Design
I need to replace my tank as well (old one failed) so along with a new filter I've been rethinking the design of my filtration setup. With the Oase's built-in removable pre-filter (now at approx. 20ppi) I'd like to change my in-tank pre-filter to extremely coarse: 10ppi. In fact, I've always wanted the coarsest in tank pre-filter I could get but unfortunately could only ever readily source 30ppi cylindrical sponges. My thinking is all I want the in-tank pre-filter to do is to prevent the intake strainer from getting clogged and obstructed for as long as possible before needing to be cleaned. I think 10ppi would do that better than 30ppi. Along those lines, I'm thinking a dual in-tank pre-filter - connected buy a 'T' - with two 10ppi sponges would provide even more filtration surface area and keep things flowing longer and more optimally between changes. Also, I'm concerning the efficiency of flow design/fluid dynamics it seems to me that a regular 'T' would reduce flow more due to water turbulence and a fitting of another profile ('Y' or something with a smoother transition to the main vertical intake tube) would be more efficient for water flow and GPH? This design could be just bare sponges slipped over dual strainer fittings or a caged sponge design, either the Eheim or something like it.

Lastly, does a well implemented dual pre-filter of similar design exist on the market? I prefer not to reinvent the wheel if possible.

I'm thinking this design would be great for a messy turtle tank filtering the water in this sequence:
a.) Dual 10ppi in-tank pre-filter sponges
b.) Canister filter's easily removable pre-filter stack with 12-14" of 20ppi sponges
c.) Canister Filter's first media basket filed with 30ppi followed by 60 ppi sponges for additional mechanical filtration and biological filtration (60ppi to remove the finest particulate before the water passes onto the biological media baskets - the latter containing Sachem Matrix and some Fluval Biomax rings - to keep the biological media as clean as possible and prevent its pores from clogging by particulate.
d.) 4 media baskets with biological media (75% Matrix and 25% Fluval Biomax rings).
e.) Finally media basket filled with a medium sponge (30ppi?) - perhaps charcoal infused?) to protect impeller and final filtration.

Any thoughts?


  • Eheim 4004320 Two Pre-Filters and T Connecter.jpg
    Eheim 4004320 Two Pre-Filters and T Connecter.jpg
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