How to achieve max mix of clean and dirty water within the display tank?

[taneal1]

I'm looking for a generic answer to provide a starting point for determining the optimum input/output pipe locations. Ignore any other requirements/desires due to the various tank filter types, e.g. sump, canister, HOB, sponge, etc. Under these conditions, what would be the optimum locations within the display tank for the "clean water" input and the "dirty water" output, that would achieve the best water mix. i.e. No "dead spots" where the dirty water would tend to accumulate, rather than be replaced quickly with clean water.

I find myself wondering what factors are at play here, that would determine the water flow pattern(s). Probably an oversimplification, but for a square tank, it would seem that an input at the top and close to one side, and an output at the bottom and close to the opposite side, would provide the best mix.

If for no other reason than I AM a curious person who likes to experiment... Whatever final setup I choose, I plan to add something to color the clean input water and observe how it mixes with the dirty tank water.

Thanks for any thoughts/info,

Tom

[bluelagoon]

The out put usually goes near the surface for greater oxygenation,since that is where the gases inter the tank.The intake in near the bottom usually on the other side of the tank.Some filtered and some unfiltered water will be coming and going.I have a 6 footer that I keep the out put in the center shooting water to both ends.

[Adam S]

To add on to what Mervin said (all of which was correct), filtration and flow are separate things. A filter running at 10x per hour isn't necessarily better than a filter running 3x per hour with a circulation pump imo.

[Paul Sabucchi]

Generally if you have the output from the filter at the top of a short side pointing along the surface and the outflow to the filter towards the bottom of the same short side you get a kind of circular flow (along the surface, down the opposite short side and back along the bottom)

[taneal1]

The out put usually goes near the surface for greater oxygenation...

Mervin,

Thanks for the info, and I agree with you regarding oxygenation.

However, in my post I stipulated that the *only* factor to be considered was the optimum mixing of clean and dirty water.

[taneal1]

Generally if you have the output from the filter at the top of a short side pointing along the surface and the outflow to the filter towards the bottom of the same short side you get a kind of circular flow (along the surface, down the opposite short side and back along the bottom)

Thanks Paul,

This is exactly the type of info I'm looking for.

Now, if the tank input and output locations in your example were exchanged, presumably the *same* "circular flow" pattern would exist, but in the opposite direction, and still provide maximum mixing of clean and dirty water. If so, then for mixing purposes *only*, the top v. bottom locations are irrelevant.

With the water mix factor now determined, the next task would be to develop a list of advantages and disadvantages for the locations of display tank water inputs and outputs. This would allow tank setups to favor the priorities desired by the individual.

As an example, using info already stated, locating the tank input near the surface and angled upward increases oxygenation. On the other hand, locating the tank output at the surface would provide water surface skimming.

TANK OUTPUT - Surface
ADVANTAGES:
Skimming

DISADVANTAGES:
Oxygenation not improved (Alternate: Airstone)

Any additional info regarding advantages/disadvantage of tank input/output locations is greatly appreciated. I will certainly use any data in determining my new tank setup, and it should help others doing the same.

Tom

[Paul Sabucchi]

At that point you have to consider what type of filtration you are using, with a sump you will be forced to have the outflow from the surface (overflows) and that will provide surface skimming. With a canister you can decide where to position in and out, but placing the outflow to the filter too close to the surface risks getting air-bubbles in.
For the purpose of water circulation in the tank it can be boosted with wavemakers, some say discus prefer next to still water, in my 100gal I have a 540gal/h wavemaker on 24/7 because the discus are happier with it.
Another consideration is if you want all the residues swept towards the intake of the filter (the tank looks nice and clean but the filter gets full of rubbish), or to have it accumulate somewhere else, where it will be more if an eyesore but easier to temove by syphoning

[bluelagoon]

In most cases it should tell you on the packaging on how to set up a canister for best flow/results.They have probably done this in their labs.

[taneal1]

At that point you have to consider what type of filtration you are using, with a sump you will be forced to have the outflow from the surface (overflows) and that will provide surface skimming. With a canister you can decide where to position in and out, but placing the outflow to the filter too close to the surface risks getting air-bubbles in.

Thanks, Paul.

I completely agree with your statements. Any information I obtain will be used to decide whether I want to use a canister or a sump. In the past, canisters have worked just fine for my needs, so I've never used a sump. This will be my first discus tank and I want a setup optimized for their health and development.

Rather than limiting my options to a specific filtration system e.g. canister, sump, HOB, sponge filter or whatever, and then abiding by those requirements, I'd like to first determine the optimum choices from all options, and then choose the most advantageous filtration system.

Is there a consensus as to the optimum filter system for discus?

Tom

[dagray]

I run an HOB (hang on back) AquaClear 110 on the left side of the tank and a Fluval 406 with the intake toward the bottom of the middle of the tank and the output blowing on the glass on the right side of the tank. This allows vertical circulation on the left side of the tank and horizontal circulation throughout the tank.

Another consideration is your decoration and plants as they will block circulation. I have a big stump in the center of my tank and it affects the flow, but I have no dead spots in the tank. I do have a couple areas of low flow which the marble hatchets love to hang out in.

[Cove Beach]

In my case I have a 72”tank with a center overflow draining to a basement sump. My return is split with an output on each end an inch below the surface and on a 45deg. angle both down and towards center of the tank, I use a pair of gyre pumps to push water down and towards the front glass which sweeps detritus up the front glass and across the surface into the overflow. Nothing sits on the bottom, and the pumps run at 30%. The discus like to play in the flow.

[taneal1]

I have a big stump in the center of my tank and it affects the flow, but I have no dead spots in the tank. I do have a couple areas of low flow which the marble hatchets love to hang out in.

Thanks Dave,

Have you determined the "areas of low flow" by observing the fish or by other means?

Tom

[taneal1]

My return is split with an output on each end an inch below the surface and on a 45deg. angle both down and towards center of the tank

Splitting the return is a great idea!

I use a pair of gyre pumps to push water down and towards the front glass which sweeps detritus up the front glass and across the surface into the overflow. Nothing sits on the bottom, and the pumps run at 30%.

You've obviously put a lot of thought into flow patterns, which is exactly what I'm looking for. Where are the "gyre pumps" located?

The discus like to play in the flow.

I've encountered a number of similar comments. Despite the still waters of their origin, it appears that discus have no issues with moving water...

Thanks for all the info,

Tom

[dagray]

Thanks Dave,

Have you determined the "areas of low flow" by observing the fish or by other means?

Tom

By observing the flow of flake food on the surface of the water..

[JamesW]

These are good things to think about but at the same time it might not be as critical as you think. Water mixes and 'dirtiness' diffuses. You are turning over the water volume anywhere between 3 to 10 times an hour. If you have ever dosed with a color medical treatment you'll see that the dye is evenly distributed after ~5-10 minutes. A low flow area might actually help by allowing poop to settle in a single area for easy removal and avoid it getting into your filtration setup.

I have a corner overflow skimming the surface on the left back corner and the return on the right back corner pointing down. Directly underneath the return I have a wavemaker directed towards the front glass and another wavemaker about halfway across the tank directed towards the front left bottom corner of the tank. Poop accumulates in one or two spots allowing for easy removal.

Obviously you shouldn't have your filtered water output aimed directly at your dirty water intake but for almost any other setup it'll probably work well enough.