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Discussion Starter · #1 ·
I've got a sump running a variable speed DC return pump. Its rated up 8000LPH and is on a 400L system, so up to 20x turnover.

I'm curious whether it's possible for me to have too much flow. To essentially push the water through the sump and media so fast that it becomes inefficient in breaking down organics due to lack of dwell time.

I've currently got it running at 50%, so about 10x turnover.

Any thoughts?
 

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For many reasons I would stick with the 10x turn over; less if possible. How are you returning the water to the tank? Experience has shown Black Beard Algae seems to grow best in high flow areas.
In many setups, a wide spray bar along the back of the tank giving a nice even flow (without the plants moving a bunch) seems to work the best.
 

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Nature does 100% flow. Most aquarium plants are from streams not ponds or lakes. A higher flow just brings more food to the bacteria on the media. You also raise the Oxygen level making for a healthier aquarium- who doesn't like to breath easy?
I'm not convinced that high flow and aeration ruins Co2 levels...if anything that flow brings more bubbles to each leaf. But,I never have used Co2 and that's just my view of it and flow.
Now,super high flow in nature? Almost always devoid of plants for physical reasons...any rock or wood rips into a rooted plant OR a mountain runoff has zero nutrients and killing fast movement.
 

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Discussion Starter · #4 ·
Immortal, the water’s returning through a central return line that tees off sending flow to the left and right side of the tank from the centre weir. Flow runs along the back wall, hits the side and bounces back to the centre. Easiest to see in the photos below.

A wide spray bar would be possible, but I’d rather not mess around with it. Bouncing the flow off the side of the tank seems to give a nice broad flow.

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Stan, I don’t doubt more flow brings more organics to the media, but I wonder if it’s processed efficiently if it passes through to quickly.
 

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IMO you are thinking about this wrong. Unless you're flow is too much to the point it damages plants, it kind of doesn't matter. Especially with fast growing plants like stems, they will consume a large percentage of the waste, if not all, hence why we need to add fertilizers.

With that, a filter will most likely have the highest concentration of bacteria, but between soil and other surface areas in a planted tank, most reasonably stocked tanks can get by with what is in the tank alone plus flow. I have successfully had a 7 gallon cube with dense crypts, moss, and over 60 trout goodeids. This was not optimal, and I didn't even realize i had that many, but the tank and fish were healthy with one of those azoo hob filters with a little matrix in there and the aquasoil. They have since been moved to an 80 gallon.

One of the biggest benefits for me with having excess media in my sump is the ability to spread out the bacteria. This allows me to insta cycle a new tank, for myself, a QT, or to get someone new into the hobby. But in removing that media, I am not shocking my system. Additionally, as you tank ages and stuff gets dirty, there is a buffer zone.

Back to flow, the way media works, is it is porous. So even if water hits it at speed, only so much can flow through it so quickly. And while saltwater and freshwater bacteria are different, my bacteria in my reef has no problems handling my tank at 100x turnover. Even a FX6 is pumping 500gph or so through a 5 gallon bucket, so 100x turnover give or take for canisters. All of these combined are why I believe high flow with regard to the filtration process is a largely irrelevant question in a real world aquarium setup.
 

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Immortal, the water’s returning through a central return line that tees off sending flow to the left and right side of the tank from the centre weir. Flow runs along the back wall, hits the side and bounces back to the centre. Easiest to see in the photos below.

A wide spray bar would be possible, but I’d rather not mess around with it. Bouncing the flow off the side of the tank seems to give a nice broad flow.

View attachment 1027296

View attachment 1027297

Stan, I don’t doubt more flow brings more organics to the media, but I wonder if it’s processed efficiently if it passes through to quickly.
Thats actually a decent setup - should give a nice swirl effect on each side. In your case, it's a little hard to tell, but it looks like the right hand output is more of an open pipe where the left hand side appears to be a pinched down nozzle. An open pipe on each end would give you the same flow, but with less velocity - just an option.
 

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There is no such thing in this hobby of over filtering or too much quality media. Its a safe buffer for the "One more fish" syndrome. In fact,I wish there more great filters shown on aquarium boards. UV filters should also be talked about more. If they work as advertised? More buffer for those who don't quarantine. Most don't!
 

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I say go with 10x flow. Much faster than that and you'll be running a whirlpool, not an aquarium. I would rather have too much flow than too little flow.
 
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