Fluval 407 and pot scrubbers

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Airborne 82nd

Aquarium Advice Regular
Apr 16, 2024
Mount Olive NC
I'm thinking of converting my 407 from matrix to scrubbers. Does anyone know how many scrubbers will fit in a tray? Here is plan (A) leave the bottom tray full of the stock black course sponge then slowly one at a time change the other three trays over. I'm thinking one tray per month. Then it hit me why not do it all at once? So plan (B) I have a tidal 75 hob that has a bag of matrix in it. Could I just leave the sponge in the bottom of it and pack the hob full from the 407 matrix? I would need to weigh it out but I think I can get 6 to 7 pounds in the hob. This is my 75 gallon tank that has about 70 gallons of water in it. If my math is correct this should give me at least 1 kg to 100L? 1kg 2lb from hob 3kg 6lb from the 407.
A couple of side notes age of matrix. The bag in the hob was hooked up in week one of Jan. the cycle was complete March week 2. The three trays in the 407 have been in it as of April 24. What have I missed? Good idea or waist of time?
One of our members from a few years back was a big fan of pot scrubbers for bio media.

He recommended 16 pot scrubbers per tray for a SunSun 303b which is an equivalent size filter to a 407. I would work on somewhere in that region.

I would go with option A. If you went with option B, you would be removing half your biomedia when you eventually remove the HOB. With option A, you are only removing 1/3 at any one time. So option A would have less of an effect on your cycle. Belt and braces would be Option B, run them both for a couple of months, then slowly remove the media from the HOB over a 3 or 4 weeks instead of just removing the filter in one go.
OK I'm ready to start the change on my 407. I bought 20 scrubbers this should be enough for one tray and let me know how many more I need. But after reading that article (thank you) I think I will end up using all four trays and stay with the two large stock prefilter. I will change them one at a time. Do you think I should start at the top and work my way down? This filter flows from the bottom up.
I also will leave the Tidal 75 setup with one course sponge on the bottom 2 inches of floss and a cycled 1 lb. bag of matrics. There is no rush on this it is just time to look at the inside of the 407 so I thought why not start now. Open for any ideas.
Thank Airborne
I would start at the top and work down as you suggest. It seems intuitive to me that the microbes will spread out from the bottom to the top in the direction of water flow, so having the new media last will get it to establish quicker.

You may have already read this, but this article is where most of the pot scrubber use originates from. I was going to give them a try myself at one point, but you cant buy plastic pot scrubbers in the UK for some reason i can't fathom. So i gave K1 a try instead based on that site, which seems to work fine.

Ive not always been the biggest fan of the site or its author, but the more first hand experience i get the more my experience lines up with what he says.
I did see that write up the one you wrote me about before led to the other part. At my level you read all you can just have to read between the lines. A lot of quackery and snake oil out there. Putting the scrubbers in Sat I'll give them a good wash in a bucket of tank water. I can't wait to see how those two big prefilter look in the 407 it's been 47 days but still a lot of flow from the output. This will give me a place to start + or - for maintenance schedule. Still have to consider the pump.
Thanks for the help
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