Does good 'flow and distribution' always require high current?

[Wookii]

Hi @Wookii

I am 100% with you on this. It is perfectly conceivable to have a filtration inlet and outlet combination where 'pockets' of water are stationary. A spray bar will help with distribution of water on the way into the tank. But, you'll have to help me here - is an immersed multiple-inlet pipe then used to feed the aquarium water back to the filter? Or, do most people use a single inlet (as I do on my 125 litre tank)? If we had access to suitable-sized tanks and inlet/outlet combinations, all that would be necessary would be to put one drop of dye in the water and watch how it disperses.

JPC

I guess most people use a single inlet and single outlet per canister filter. On a larger tank they may have two canister filters and have two inlets and two outlet.

However for the purposes for designing a low velocity system, let’s just dispense with any restrictions like that. Let’s just assume we can choose any number, size, style and position of inlets and outlets as is necessary to achieve the design goal.

I appreciate any design would be dependent on hardscape also, but let start simply.

 

[Wookii]

Hi Folks,

I think a lot can be gleaned by closely observing the region in the immediate vicinity of the filter inlet(s) in the tank. How close to the filter inlet(s) do particles need to be to get sucked in? On my 125 litre tank using an Eheim Ecco Pro 130, this has caused me some concern.

JPC

I think that might be a red herring to an extent. The velocity at the filter outlets can be varied independently to the filter inlets, simply by differing the size/capacity and number of each respectively.

For example if you have 3000 litres per hour in through a single outlet and out through a single inlet, you’ll, you can decrease the outlet velocity by, for example, doubling the number of outlets, but the inlet uptake should still be the same if you kept that as a single inlet.

Now there is an argument for increasing the number of inlets to obtain more even distribution, since the distribution is achieved by both the outlets pushing water in a certain direction or pattern, and the inlets pulling the water in a certain direction.

I think if low velocity is the objective, then quite possibly the number of inlets needs to be increased so water isn’t drawn naturally to a single point in the tank.

 

[jaypeecee]

Let’s just assume we can choose any number, size, style and position of inlets and outlets as is necessary to achieve the design goal.

Hi @Wookii

In order to ensure that we're 'singing from the same song-sheet' what exactly is your design goal? It's not a 'low' velocity system, is it? Wouldn't it be more accurate to say an 'optimum' velocity system, whatever we deem to be 'optimum'?

JPC

 

[jaypeecee]

Now there is an argument for increasing the number of inlets to obtain more even distribution, since the distribution is achieved by both the outlets pushing water in a certain direction or pattern, and the inlets pulling the water in a certain direction.

I think if low velocity is the objective, then quite possibly the number of inlets needs to be increased so water isn’t drawn naturally to a single point in the tank.

Hi @Wookii

The point that you are making above is what I had in mind when mentioning my single-inlet setup. Perhaps I should have spelled it out in more detail. The thing is that a single filter inlet can only draw in particles that are in very close vicinity. Multiple inlets should be more effective.

JPC

 

[dw1305]

Hi all,

I can't access the full text at the moment, but it might be interesting to anyone who can.

I don't have access to this one either.

cheers Darrel

 

[Wookii]

Hi @Wookii

In order to ensure that we're 'singing from the same song-sheet' what exactly is your design goal? It's not a 'low' velocity system, is it? Wouldn't it be more accurate to say an 'optimum' velocity system, whatever we deem to be 'optimum'?

JPC

No, low velocity is indeed the design goal - to encourage the most natural behaviour from the tank fauna, which I seem to observe when the flow velocity is zero (i.e. filter and skimmer are off).

Obviously we can’t have zero flow, as we need the filters biological filtration (to an extent - I appreciate less so in a heavily planted tank) and we need to distribute CO2 et al to the plants with no dead spots - i.e. sufficient distribution.

So optimum distribution is a secondary design goal, albeit being counter the to the primary design goal, but the primary design goal is still achieving that optimum distribution with the lowest possible ‘velocity’.

The more I think about it, the more I think that as you reduce velocity, you more you need to increase turnover to compensate, so you are driving greater volumes of ever slower moving water around or along the tank.

In my own new tank which is relatively narrow to its length (1500 x 450 x 450) I’m thinking inlets at one end, outlets at the other - and achieving lowest velocity with sufficient distribution is dumping increased quantities of water at the outlet end via increased turnover, so the whole body of water is being slowly displaced by the slow moving mass of incoming water.

My other thought of course is that I’m just over thinking all this lol - but it’s an interesting theoretical exercise non-the-less.

 

[kilnakorr]

My other thought of course is that I’m just over thinking all this lol - but it’s an interesting theoretical exercise non-the-less.

I'm sure you are, but these discussions are how we learn and come up with new ideas.
Been following this thread closely, and just added spraybar today for a test. Have low turnover, but no dead spots as far as I can tell.
The spraybar isn't great looking but neither are powerheads. Otos and shrimps are far more active in the open areas now.

 

[Wookii]

I'm sure you are, but these discussions is how we learn and come up with new ideas.
Been following this thread closely, and just added spraybar today for a test. Have low turnover, but no dead spots as far as I can tell.
The spraybar isn't great looking but neither are powerheads. Otos and shrimps are far more active in the open areas now.

Great stuff, you’re about 10 steps ahead of me then - I think practical tests are the only real way to come up with a real design. How have you orientated the spray bar, and where is/are your inlet(s)?

 

[kilnakorr]

How have you orientated the spray bar, and where is/are your inlet(s)?

Spraybar is 'standard' full length at the back.
Inlet at back corner.
Using an older tank with drilled holes at bottom, so can't move inlet / outlet

 

[alto]

As an aside though, it would be interesting to understand why those tanks from those experienced aquarists achieve good algae free plant growth with minimal apparent velocity.

Thanks for the “experienced” accolade

But I also had maybe 2-4x flow (I never checked) on my first tanks - OK the very first tank was one of those box kits (a surprise “present”) that needed filter and lighting upgrades so I just traded that out for another kit tank (not much else available in shops at the time) that delivered much better lighting, and visibly better flow (though far from high flow), and also had a much nicer “finish”

I knew absolutely nothing about fish (and never intended to get a fish tank) when I began, but I did garden - outside -
I am still a terrible indoor plant keeper

And I began reading online and books - and a local aquarium shop owner was very interested in planted aquariums and had a copy of Takashi Amano Nature Aquarium World and other books for browsing (and the important Chair )

I did always do frequent 50% (& more) water changes - I was appalled by the concept of limited fresh water for optimum fish care

 

[alto]

Double post

 

[jaypeecee]

...the primary design goal is still achieving that optimum distribution with the lowest possible ‘velocity’.

Beautifully put! We're now on the same wavelength.

I’m just over thinking all this...

No, I don't think (!) so. I suspect there may have been some people who, at the time, suggested that Thomas Edison was overthinking how to make a commercially-viable electric light.

JPC

 

[Emil.]

I 100% agree that fish look more relaxed in the absence of flow. It would be great to have the best of both fauna and flora worlds.

One out of the box (read: stupid ) solution would be to have CO2 distributed to many tiny diffusers strategically placed underneath each non-easy plant. This brings many challenges: the amount of diffusers, the distribution itself and most annoyingly the clogging and maintenance.

Another idea: What about inline CO2 reactor and water raining down over the whole surface area?

Or! Outlet evenly “pipped” around the whole circumference at the bottom of the tank, gently spraying towards the centre, overflow on top. But would the fishies be okay with gentle but constant up flow? I assume it’s much easier for them to move forward than swim down.

I’m out of ideas for now. Please feel free to tear any/all of them down, I won’t be offended at all. Just trying to brainstorm, that’s all.

 

[jaypeecee]

I 100% agree that fish look more relaxed in the absence of flow.

Hi @Emil.

I'm only stating the obvious here but it will depend on choice of fish species as to whether or not they prefer 'high' or 'low' flow.

JPC

 

[Emil.]

I'm only stating the obvious here but it will depend on choice of fish species as to whether or not they prefer 'high' or 'low' flow.

You're right, @jaypeecee . I should have worded it better. Same as the OP, I too have observed that my fish seem to be more relaxed and inquisitive of their surroundings with lower flow.

 

[hypnogogia]

I’ve even considered whether it would be possible to have pipe work under the substrate feeding sprinkler type head at various points (hidden from view by hardscape of course) allowing slow outflow across the bottom of the tank - but the more I think about that, the more it feels like a maintenance nightmare.

Anyone have any other ideas?

I seem to remember a family friend having exactly that in cube in the eighties. Lots of tiny siphons sticking out of the substrate connected via a network of tubes that all fed into a 16/22 tubes that ran to the filter. Not sure if it was an eheim of Sicce set up. I’m not sure how long it lasted before the under substrate tubes clogged up and they needed to dismantle the lot.

 

[Wookii]

I 100% agree that fish look more relaxed in the absence of flow. It would be great to have the best of both fauna and flora worlds.

One out of the box (read: stupid ) solution would be to have CO2 distributed to many tiny diffusers strategically placed underneath each non-easy plant. This brings many challenges: the amount of diffusers, the distribution itself and most annoyingly the clogging and maintenance.

Another idea: What about inline CO2 reactor and water raining down over the whole surface area?

Or! Outlet evenly “pipped” around the whole circumference at the bottom of the tank, gently spraying towards the centre, overflow on top. But would the fishies be okay with gentle but constant up flow? I assume it’s much easier for them to move forward than swim down.

I’m out of ideas for now. Please feel free to tear any/all of them down, I won’t be offended at all. Just trying to brainstorm, that’s all.

Some good ideas here, thanks for the input. The ‘tiny diffusers’ suggestion was along the similar lines I was thinking with under substrate pipe work and sprinkler heads at ‘strategic’ points. The maintenance is a major issue with anything plumbed under the substrate, and is something I’m concerned about.

The ‘rain’ idea is an interesting one, but I suspect it’d struggle getting the CO2 rich water back down to the substrate level, especially as the outlet water would be presumably running past heaters first and would be slightly warmer than the tank water - warm water rises, so it might stay towards the top of the tank. There is also the issue of aesthetics of course in a rimless tank without canopy.

Similar issue with the substrate level perimeter spray bars, I suspect the aesthetics would kill that one. Though a top to bottom distribution is interesting.

That brings me onto @foxfish’s previous experiment of a reverse undergravel filtration system - that sounds like a solid idea to distribute CO2 from bottom upwards. I just wonder if different substrate thicknesses or other irregularities could cause dead spots. @foxfish could you go into any mor detail on how that turned out?

Keep the ideas coming though, some good input there!

 

[Wookii]

Hi @Emil.

I'm only stating the obvious here but it will depend on choice of fish species as to whether or not they prefer 'high' or 'low' flow.

JPC

You're right, @jaypeecee . I should have worded it better. Same as the OP, I too have observed that my fish seem to be more relaxed and inquisitive of their surroundings with lower flow.

Good point, and a caveat I should have thought of making myself.

My observations are limited to very small number of species I keep in my tank. For the sake of completeness that includes Ember Tetras, Pygmy Corys and Chilli Rasbora.

 

[Emil.]

My observations are limited to very small number of species I keep in my tank. For the sake of completeness that includes Ember Tetras, Pygmy Corys and Chilli Rasbora.

What a coincidence, I have pygmies and embers too. I set up a low tech tank with a sponge filter for the pygmies and they seem very happy. Had the embers not been eating pygmy food all the time, I'd move them too.

 

[Wookii]

So whilst researching hardscape layouts for longer tanks I stumbled on a video by @George Farmer at the Interzoo show in 2018. The tank, designed by Jurijs Jutjajevs is 2400mm x 300mm x 300mm and has a very unique inflow/outflow design. Obviously in the case of this tank they wanted to create a very fast flowing tank like a small stream, and are pushing 100x turnover through the tank (about 22,000 litre per hour). However I wonder how well the design might translate to what we are discussed in this thread to the extent that the inlet and outlet are both at substrate level, so CO2 and nutrient rich water might more naturally flow over all areas (subject to hardscape exclusion) of the substrate from one end to the other. Other than the obvious loss of tank real estate at either end, the design is equipment free in tank. Obviously the inlet and outlet sizes (and hnec the loss of tank real estate) could be reduced a significant amount if say 10x-20x flow was targeted in the design instead.

You can see it working in the video here (6:25 onwards):



Also in a different video (below) of George's, but at the same event, there is an other unique inlet/outlet design. The outlet appears to just have a single hole in a piece of acrylic tube in one corner pushing up through the substrate, with an outlet of similar design in the opposite corner. This is an 1800mm tank.

That said, they do use a circulation pump on one corner, and the tank does appear to have a high amount of circular flow looking at the leaf movement in the video - but its an interesting idea non-the-less: Check it out (see from 3:35 onwards):