Water Circulation - POST YOUR THEORIES PLEASE

[GoldFinger]

Hey MFKers,

I would like to hear about your experience or thoughts on the ideal flow/circulation throughout your freshwater aquariums. I’m new(ish) to the hobby but have researched how good circulation can prevent thermal layering, create currents for our fish, and most importantly lift debris from the bottom of the tank, up and into our overflows.

If we could leave surface agitation out of this thread in order to keep the focus on circulation that would be ideal, however if it’s an added feature to how your returns are directed or something along those lines feel free to mention it! Please list and/or describe how you have directed your returns, wave pumps, power heads etc to achieve the following:

1) Sufficient currents for your fish

2) flow to lift debris from tank

3) circular, laminar or other flow to direct the debris toward your overflows

Selfishly I would love if anyone has advice on my current set up. I have 305G with my returns in each corner and an external overflow in the centre. I also have a currrnt USA wave pump ready to go when I figure this all out!

 

[skjl47]

2) flow to lift debris from tank

I managed to arrange tank so that there are no zones where detritus/mulm builds up in "dead flow" zones. The main thing was to set up stepped levels. The other thing was to make an alteration to the HOB outflow.
I have tried my idea in various forms over the last couple of decades. It can be done in terms of getting the visible piles of detritus to the filter intake. I posted pictures of the tank on MFK a few years ago but there have been a few major changes to the site so those may be gone.
The tank is set up and running now but is so overgrown with plants that new pictures may not show much. The picture in my avatar is of that tank and shows a bit of one wall.

I used a 20 gallon long as a test bed. The idea was to start at a back corner with the highest level. Then have a few more levels with each slightly lower than the last. The lowest level is at the opposite end of the tank with a channel to the back of the tank where the filter pickup is located.
The first time I made this channel it was a tunnel to the back corner. Worked fine as far as flow was concerned but turned into a big issue when I needed to catch a fish. The next and current channel is open at the top.

I made the levels with glass rectangles of various heights. I used clear silicone to adhear the glass in place. While the glass panes allowed the gravel to be visible thru it, the glass could still be seen and was too unsightly.
I solved this by smearing the surfaces of the glass with silicone and while it is still tacky sprinkling a layer of fine gravel onto it. Had to lay the tank on its back to do this. Worked out pretty good and looks fine. Note- the tank, glass and gravel has to be very dry for this stage.
The modification to the HOB was fairly simple. There was some scrap vinyl house siding laying about. I eventually cut a piece and glued it to the outflow of the filter. It catches the water and directs to the opposite end of the tank. So even with a basic HOB was able to get all the large detritus to move to the filter pickup.

 

[skjl47]

Hey MFKers

Hello; This greeting always gives me pause because of the optional interpertations which I will not mention. But Hey.

 

[Vampire fish]

circulating water provides nutrients essentially to "beneficial bacteria" which is key to a healthy environment.

 

[Fish Tank Travis]

The first picture shows where my returns are located. The second picture shows where the returns are currently pointed. They are in a bit of a cross direction. The tank is a 220 (6x2x2.5H) and is currently flowing about 1600gph.

However, the addition that had the biggest affect on detritus being kicked up off the bottom and into the filter was the vulture catfish. They are always active (unless I come up to the tank) and constantly swim around the bottom with their strong tails, which kicks up all of the detritus.

 

[pacu mom]

I love venturi returns. The flow direction can be adjusted just by turning the nozzle, and with the venturi effect, the flow is increased.

One venturi nozzle on the right side of our tank in conjunction with a big pump (Hammerhead), results in a very swift current that quickly traverses the 8' length of our 300 gallon tank, ricochets off the left wall and eddies near the middle of the tank near the back wall.

Here's a really old video at the end of a water change. The strong current is visible.

Tank maintenance is not our thing, so we went bare floor with vertical uptake pipes just off the floor (poop suckers) for great mechanical filtration. The tank is plumbed so that by opening a valve to a dump drain outside, we can quickly drain the tank. Opening another valve to a 55 gallon holding tank allows us to painlessly refill the main tank. (we also turn the hot/cold water on to refill the holding tank)

 

[ChrisO11000]

I try to have 10 times the display volume to be circulated an hour. I find the higher volume my system is (ie. sump volume) the better everything works. I keep a bare bottom tank to better watch for depbri.

 

[GoldFinger]

I love venturi returns. The flow direction can be adjusted just by turning the nozzle, and with the venturi effect, the flow is increased.View attachment 1285866

One venturi nozzle on the right side of our tank in conjunction with a big pump (Hammerhead), results in a very swift current that quickly traverses the 8' length of our 300 gallon tank, ricochets off the left wall and eddies near the middle of the tank near the back wall.

Here's a really old video at the end of a water change. The strong current is visible.

Tank maintenance is not our thing, so we went bare floor with vertical uptake pipes just off the floor (poop suckers) for great mechanical filtration. The tank is plumbed so that by opening a valve to a dump drain outside, we can quickly drain the tank. Opening another valve to a 55 gallon holding tank allows us to painlessly refill the main tank. (we also turn the hot/cold water on to refill the holding tank)

I love how your pacu just engulf themselves in the flow/bubbles haha.

 

[Lepisosteus]

First your not going for laminar flow you would be trying to make turbulent flow. Just a froude number calculation. Froude>1. If you are doing laminar flow all debris will settle as planar beds. Turbulent will keep most things moving or into suspension through saltation, lift vs gravity, stokes law. Turbulent conditions will result in a cleaner tank. Anyways. For a freshwater system I aim for 5-10x turnover in the sump then usually add one good size power head at 5x-10x max circulation on either side. So a 300 gallon I would put around 1500-3000gph through sump then another 3000gph-6000gph in circulation on the sides. Personally for your tank I would do around 2500 through the sump. Then supplement with 3 koralia 1500gph placed one on each end and one in the middle. For my reef system I’m running 16x turnover through the filtration which is just a coarse and fine sponge, and phosbond. Then in the tank I’m running 36x turnover in power heads. With all that I feel I should add one more power head. My rock structure isn’t the greatest but looks good.

 

[GoldFinger]

First your not going for laminar flow you would be trying to make turbulent flow. Just a froude number calculation. Froude>1. If you are doing laminar flow all debris will settle as planar beds. Turbulent will keep most things moving or into suspension through saltation, lift vs gravity, stokes law. Turbulent conditions will result in a cleaner tank. Anyways. For a freshwater system I aim for 5-10x turnover in the sump then usually add one good size power head at 5x-10x max circulation on either side. So a 300 gallon I would put around 1500-3000gph through sump then another 3000gph-6000gph in circulation on the sides. Personally for your tank I would do around 2500 through the sump. Then supplement with 3 koralia 1500gph placed one on each end and one in the middle. For my reef system I’m running 16x turnover through the filtration which is just a coarse and fine sponge, and phosbond. Then in the tank I’m running 36x turnover in power heads. With all that I feel I should add one more power head. My rock structure isn’t the greatest but looks good.

Thanks very informative. I am going to look further into implementing some of this with more questions to surely follow!