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

Wookii

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Good 'flow and distribution' is a mantra I see throughout this forum, along with the regular suggestion of filter (or circulation pump) capacity of 10x tank volume, particularly with respect to high tech tanks to achieve sufficient circulation of injected CO2 and fertilisers to all areas of the tank.

Whilst this makes perfect practical sense to me, I can't help but notice that this often results in a fair amount of 'current' throughout most of the tank - in my own aquarium, in a circular pattern around the tank, obviously most strongly in the face of the tank adjacent to the filter outlet.

I also observe in my own set-up, that when I switch off the filter and the current stops, there appears to be much more natural and exploratory behaviour from the shrimp and fish (and I think not just because they associate the lack of current with feeding times). The still water version of the aquarium makes for a much more interesting viewing experience than the running water version.

With this in mind, my question is, is it possible to design a system that achieves good flow and distribution of CO2 and ferts, without the high current?
 

kilnakorr

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Following this one.

I personally struggle with this myself.
The high flow to deliver nutrients to the plants makes sense, but I hate the looks. Especially in larger/longer tanks, where you need really high flow to get the flow to the other end (or several smaller powerheads).

I'm so open for ideas (but not spraybars as they require massive filters)
 

Sammy Islam

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I think not many of us actually achieve a 10x turnover, most probably only like 5x, but makes sense to aim for 10x as by the time the filter has media inside and gunk its probably half that.

For my tank that's full of rotala at the back i have to be careful not the stunt it from battering it with harsh flow. So for me flow pattern/circulation is probably more important. As long as i have decent flow and co2 and ferts are reaching all my plants then i should be good regardless of how quick it is going around?

Also a similar thing with increasing co2 and flow. The whole drop checker v "1 point drop", by the time we reach a "1point drop" the drop checker is most likely yellow when we are suppose to be at green. Then when problems start like co2 related algae we up the co2 even more and stress the fish and it seems like a never ending battle even though we have "more" co2 than we are "supposed" to.
 
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kilnakorr

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As long as i have decent flow and co2 and ferts are reaching all my plants then i should be good regardless of how quick it is going around?
That is exactly what is needed.
However, I have yet to find a solution were I can get a nice gentle flow all over.
I cannot seem to get a gentle sway in one end without a storm at the other end.
Main problem in my case, is that flow needs to be started at the opposite end of the tank to avoid blasting stemplants around.

I guess both @Wookii and myself are looking for solutions to generate gentle flow.
 

Zeus.

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With this in mind, my question is, is it possible to design a system that achieves good flow and distribution of CO2 and ferts, without the high current?

Yes, its having a variable flow/current in the tank. So flow is optimal to suit the plants needs at different times of day, the first 4-5 hours of the photoperiod are the most critical as thats when plants uptake the most CO2 so good flow and stable [CO2] is the key, but after plants slow down their uptake the flow/current can also be reduced as well IMO. I achieve this with Twin Maxspect Gyres which have a controller with 24 slots in a schedule so flow can be varied between 0-100% in 5% increments so towards end of photoperiod flow on restively low and at night on gentle flow, as soon as CO2 comes on flow ramps up ready for lights coming on. Having twin Gyres helps too as at night one can be off of a couple of hours at a time and cleanup crew do their work. During the day havings them alternate output moves the dead spots around also.
 
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I am in the midst of experimenting. I mashed together a spray bar and I’m happy with the mist of Co2 reaching all areas of my flex 57 but I don’t ever we see any of my Neo or Amano shrimp in the front of the tank. I would think a desirable effect is complete Co2 dissolved in the water column then high flow to drive Co2 bubbles down is not required. Nutrients I believe are much easier to distribute as eventually the mix is homogenised.
 

Wookii

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To be honest part of me asking the question - along with the observation of the behaviour of the occupants of my current tank - is that I have recently acquired a new 1500 x 450 x 450 tank, and want to plan such a low current design.

So running some ideas off the top of my head.

If we take my new tank as an example, thats 300 litres. A common configuration would be to have an inlet and outlet in two opposite corners. So assuming 10x turnover, that’s 1500 litre per hour out of each outlet.

That going to create a high level of current out those outlets, but probably achieves decent distribution via a circular flow.

If we increase the number to outlets to, say, three in each opposite corner at different heights (let’s ignore the practicalities for now - this is a theoretical exercise for the moment), we reduce the output of each to 500 litres per hour. That should see the current significantly reduced.

The problem is, the current my be insufficient to maintain the circular flow, and dead spots could be created.

So how about we put all six outlets at one end, each on a slightly different azimuth and elevation (to give even spread across the tank width and height) and have all the inlets at the opposite end. If we are maintaining our 10x turnover, then we should have less dead spots, as 3000 litres of water is entering the tank at one end, and leaving it at the other, every hour - like a wall of water travelling completely down the tank. Our only possible issue now, is hardscape causing dead spots along that line of travel, no? (I’m quite sure there are things I haven’t even thought of here, I’ve just thinking [writing] aloud).

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?
 

Wookii

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I think not many of us actually achieve a 10x turnover, most probably only like 5x, but makes sense to aim for 10x as by the time the filter has media inside and gunk its probably half that.

I agree - I suspect the 10x rules has been lost a little in translation, and is more guidance for selecting a pump/filter canister rated for 10x the tank volume, though in reality it will never deliver that.

In my own tank I’m running a filter allegedly rated at 20x my tank volume (though I don’t believe it is anywhere near that in real use) plus an in tank skimmer - so I am over egging the pudding a bit anyway.

For my tank that's full of rotala at the back i have to be careful not the stunt it from battering it with harsh flow. So for me flow pattern/circulation is probably more important. As long as i have decent flow and co2 and ferts are reaching all my plants then i should be good regardless of how quick it is going around?

That’s kind of the point though we want flow to ensure the good stuff reaches that plants, but we (I) want to achieve that with the minimum of ‘current’ (by that I mean the maximum speed/pressure of water at any one point).

Also a similar thing with increasing co2 and flow. The whole drop checker v "1 point drop", by the time we reach a "1point drop" the drop checker is most likely yellow when we are suppose to be at green. Then when problems start like co2 related algae we up the co2 even more and stress the fish and it seems like a never ending battle even though we have "more" co2 than we are "supposed" to.

To be fair the CO2 side is a different topic - I found having a good quality Ph monitor/probe has been a god send in sorting that out and eliminating the 2 hour drop checker delay - but thats for another thread.
 

Wookii

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Yes, its having a variable flow/current in the tank. So flow is optimal to suit the plants needs at different times of day, the first 4-5 hours of the photoperiod are the most critical as thats when plants uptake the most CO2 so good flow and stable [CO2] is the key, but after plants slow down their uptake the flow/current can also be reduced as well IMO. I achieve this with Twin Maxspect Gyres which have a controller with 24 slots in a schedule so flow can be varied between 0-100% in 5% increments so towards end of photoperiod flow on restively low and at night on gentle flow, as soon as CO2 comes on flow ramps up ready for lights coming on. Having twin Gyres helps too as at night one can be off of a couple of hours at a time and cleanup crew do their work. During the day havings them alternate output moves the dead spots around also.

Variable flow is a good idea to have period of lower current - but in the first instance I want to see if there is a solution for having constant low current.

Out of interest do you notice different behaviour of your fish and shrimp when the current is reduced?
 

foxfish

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I set up a low water movement tank a few years back, it was based around an under gravel filter with reverse flow.
I just used an external C02 reactor and fed the C02 enriched water up through the gravel.
It was still quite a high flow rate but due the upward diffused flow there was very little visible movement.
In fact I made a short video that is on this forum somewhere.
 

kilnakorr

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I rewatched this video on filtration last night.

In short, they say to stuck filter with lots of bio media, and for bigger tanks and a turnover of 2-3 times is enough.
 

foxfish

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You only have to think about it in a logical way, if you are injecting C02 and you want that C02 to reach all the plants in the tank, then you need to distribute the enriched water amongst all the plants.
If you only have one plant then you would only need to direct the flow to that plant but if you have a big tank full dense foliage that you need a very good and evenly distributed flow.
 

Zeus.

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I rewatched this video on filtration last night.

In short, they say to stuck filter with lots of bio media, and for bigger tanks and a turnover of 2-3 times is enough.

They have such amazing tanks, there are even better if you visit the showroom so the vid does suck you in, then they land the sales pitch

However I completely disagree about the bio media bio media for fluval 305. Medium course sponges all the way. They do forget to mention the largest bio filtration in their tanks- the plants roots

Notice they choice of ferts -ADA most expensive ferts per ppm of nutrients on the planet!!
upload_2020-4-28_8-48-1.png


As for the flow well having seen there tanks I was amazed at the low flow and it works for them, maybe its to do with the re mineralised RO water, or the excellant maintenance regime.

Dont be drawn by the sales pitch, follow the science ;)
 

jaypeecee

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Hi Folks,

Interesting thread.

I have a bit of a problem with terminology here. Specifically, flow and current. For me, they are one and the same. But, I suspect that the word 'current' is being used here to denote rate of flow, i.e. the velocity/speed at which the water is moving. I think of flow or current as electrons in a wire or water in a pipe. High flow can be achieved by 'pushing harder', be that the battery voltage or water pressure. It seems to me that, perhaps, what is needed in an aquarium is a large volume of water moving relatively slowly. Not a small volume of water running a 'four-minute mile'. I'm looking at this with a view to obtaining optimum CO2 and ferts distribution. Am I on the right track?

JPC
 

Wookii

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You only have to think about it in a logical way, if you are injecting C02 and you want that C02 to reach all the plants in the tank, then you need to distribute the enriched water amongst all the plants.
If you only have one plant then you would only need to direct the flow to that plant but if you have a big tank full dense foliage that you need a very good and evenly distributed flow.

Agree completely - the need to distribute the CO2 isn’t under question. The question is, is there a way to do this where the current/speed/velocity of the water is slow, rather than the typical single point source high velocity filter outlet. Your under gravel system was a perfect example, but there must be others.
 

Wookii

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I rewatched this video on filtration last night.

In short, they say to stuck filter with lots of bio media, and for bigger tanks and a turnover of 2-3 times is enough.


They have such amazing tanks, there are even better if you visit the showroom so the vid does suck you in, then they land the sales pitch

However I completely disagree about the bio media bio media for fluval 305. Medium course sponges all the way. They do forget to mention the largest bio filtration in their tanks- the plants roots

Notice they choice of ferts -ADA most expensive ferts per ppm of nutrients on the planet!!
View attachment 134012

As for the flow well having seen there tanks I was amazed at the low flow and it works for them, maybe its to do with the re mineralised RO water, or the excellant maintenance regime.

Dont be drawn by the sales pitch, follow the science ;)


I think the Green Aqua videos are great, really well put together and professionally produced, and Balazs is clearly a charismatic presenter - but I agree, you do have to see ‘through’ some of the marketing - which is fair enough I guess, they’re not doing them for charity!

I don’t want to get too hung up on the turnover thing - as @foxfish says, it’s a simple requirement to get CO2 and nutrient rich water to all plants in the aquarium. As @Zeus. says, the plants are the main biological filters, so as long as waste is being sufficiently processed, and full distribution of CO2 etc is being achieved, actual turnover shouldn’t matter,

The question again to reiterate, is can we achieve that manner with low current/velocity?
 

foxfish

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I did another one with a matrix of pipes on a bare bottom tank and potted plants, unfortunately the videos were on photobucket and I can’t find the originals as they were stored on an old laptop long buried .

Anyway the standard way of using a full length spray bar is designed to move the water column as a whole mass.
The concept is to push the water along the surface and down the front glass along the bottom and back up the rear.
If you can get that rolling effect then I think you will have good success.
 

Wookii

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Hi Folks,

Interesting thread.

I have a bit of a problem with terminology here. Specifically, flow and current. For me, they are one and the same. But, I suspect that the word 'current' is being used here to denote rate of flow, i.e. the velocity/speed at which the water is moving. I think of flow or current as electrons in a wire or water in a pipe. High flow can be achieved by 'pushing harder', be that the battery voltage or water pressure.

I don’t think if ‘flow’ and ‘current’ as being the same thing - a large river can have high flow, and low current, and a small stream can have low flow and high current. I think of flow as volume, and current as speed/velocity/turbulence.

Thats said, I don’t want to split hairs too much on definitions, though I do agree, I didn’t like using the term ‘current’ - I just couldn’t think of anything else. Velocity, now you’ve used it your post, is much more appropriate.

It seems to me that, perhaps, what is needed in an aquarium is a large volume of water moving relatively slowly. Not a small volume of water running a 'four-minute mile'. I'm looking at this with a view to obtaining optimum CO2 and ferts distribution. Am I on the right track?

JPC

Yes, I think you are on the right track - varying the volume could help achieve greater distribution, if our aim is to reduce the velocity. However I think we also need to consider the outlet design - starting with a blank piece of paper - in how we achieve sufficient distribution with low outlet velocity.
 
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foxfish

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