Water flow in the planted aquarium?

ulster exile

Member
Joined
6 Jul 2007
Messages
350
Location
Birmingham, UK
Thank you ceg for your most informative reply - I would love an external, but space is an issue tbh. I do however have 4 glass diffusers (cheapos from fleabay) so I could easily split the CO2 into two tubes and have a diffuser at either side. I may look at upgrading my filter to increase overall flow rate as well and extend the spraybar to increase distribution of the flow.

Apologies to Dev for spamming his thread, it never even occurred to me as I posted, however I am grateful you started the topic :)
 

Steve Smith

Member
Joined
19 Jul 2007
Messages
4,421
Location
Leamington Spa, UK.
No worries, you're not spamming :p I was just interested to see how Ed built it, but thought it might benefit others under its own specific thread (easyier to find :))

I'm going to try to get to my local DIY place tonight or tomorrow night and suss out parts.
 

Steve Smith

Member
Joined
19 Jul 2007
Messages
4,421
Location
Leamington Spa, UK.
Thought I'd just add a quick question to this post... See what other people do etc :)

Ok, so running the 2 filters with spray bars shooting back to front on the level, I wonder what is the best configuration for the inlet tubes. Currently I have one in each corner. I wonder if having both in the same corner (at differing heights perhaps) may draw water accross the length of the tank.

The problem is that I'd like to have bushy plants in one corner (bacopas etc) and then "fluffy" plants in the other (mayaca). As it is at the moment the mayaca seems to catch a lot of debris.

Any thoughts on this?
 

ceg4048

Expert/Global Moderator
Staff member
Joined
11 Jul 2007
Messages
8,993
Location
Chicago, USA
Hi Steve,
The flow patterns are mostly going to be determined by the outflow velocity. Inflow pipes pull water from every angle in more or less a spherical pattern. As a result the pressure difference and it's flow velocity from any one angle is low. By comparison, the outflow is coming from only one angle, i.e. lily pipe or spraybar so the velocity from this single angle is high. Having inflow pipes together may have some effect but I don't think it will appreciably affect the flow distribution. Any bushy plant, or any plant that has a high density of individual leaves will trap debris. It's an annoyance but that's just life. Fluff the plants frequently to dislodge the debris. In fact, a standard maintenance procedure is to fluff plants regularly to dislodge debris such as detritus and algae spores that have a tendency to settle on the leaf surface.

Cheers,
 

beeky

Member
Joined
21 Aug 2007
Messages
879
Location
Chippenham, Wiltshire
I've found a good technique is to siphon off the debris from the stems so that the stem actually gets sucked up the tube. Obviously the diameter of the tube needs to be big enough and the flow not too strong. Also not a good idea if they've been newly planted! Raising the bucket off the floor (chair is ideal) reduces the flow enough I've found.
 

clint24

Member
Joined
16 Mar 2008
Messages
44
Location
Bromley, Kent
Hi to all.I have a lily pipe in my 60cm tank & after reading this topic I am thinking about changing my lily pipe for the aquili 21 inch spray(AE sells them).Would this be too long for my 60cm tank & would it better to split my 13mm pipe(with a Y branch) & fit either 2 x 9mm or 2 x 12mm intake pipes.Or do you recommend a different setup.cheers.
 

JamesM

Member
Joined
17 Apr 2008
Messages
1,913
Location
The BIG End, South Wales
About the spray bar - AE state its 21 inches, so it *should* be fine in a 60cm tank.

Email Richard at AE to see if thats the overall length or just the spray section. Should be ok either way though :)
 

plantbrain

Expert
Joined
2 Aug 2007
Messages
1,946
I've looked at ADA's flow and store front displays etc for some time and modified things to enhance things.
I want good flow, but not plants being blasted around either, same for fish for the most part.

The goal here is to have good low pressure, but high volume flow like we see in natural systems.

Reef folks have long used such powerheads (and they are much cheaper than in the past) these days.
I average about 14 Turnovers per hour for most of the better run tanks I've done.

Generally, the flow from the filter is amplified using the low pressure propeller type powerhead and it blast the CO2 and the filtered water all over, as well as providing good surface movement without breaking the surface.

I new and novel method to add O2 at night without an air stone:

Use a reducing tee off the return pipe and place a check valve to prevent back flow into a small air pump, place the air pump on the reverse cycle of the CO2(or a few minutes in between etc).

This will add lots of air and O2 during the night, keep things clean without adding anything inside the aquarium.
Cost is pretty cheap.

Will allow more fish and reduce the CO2 when you do not need it for plant growth.

Regards,
Tom Barr
 

teg1203

Member
Joined
17 Jun 2008
Messages
62
Location
Mid-Wales, Powys
plantbrain said:
I've looked at ADA's flow and store front displays etc for some time and modified things to enhance things.
I want good flow, but not plants being blasted around either, same for fish for the most part.

The goal here is to have good low pressure, but high volume flow like we see in natural systems.

Reef folks have long used such powerheads (and they are much cheaper than in the past) these days.
I average about 14 Turnovers per hour for most of the better run tanks I've done.

Generally, the flow from the filter is amplified using the low pressure propeller type powerhead and it blast the CO2 and the filtered water all over, as well as providing good surface movement without breaking the surface.

I new and novel method to add O2 at night without an air stone:

Use a reducing tee off the return pipe and place a check valve to prevent back flow into a small air pump, place the air pump on the reverse cycle of the CO2(or a few minutes in between etc).

This will add lots of air and O2 during the night, keep things clean without adding anything inside the aquarium.
Cost is pretty cheap.

Will allow more fish and reduce the CO2 when you do not need it for plant growth.

Regards,
Tom Barr

Would it be possible to utilise the co2 diffuser by swapping from pressurised co2 to air (from a small pump) via a simple tee and check valve and operate "crossover" fashion so when one is off the other is on and vice versa.
 

a1Matt

Member
Joined
10 Mar 2008
Messages
2,497
Location
Bromley
teg1203 said:
Would it be possible to utilise the co2 diffuser by swapping from pressurised co2 to air (from a small pump) via a simple tee and check valve and operate "crossover" fashion so when one is off the other is on and vice versa.

Interesting idea Teg, and the same thing sprang to my mind as soon as I read Toms post. For me though I think it would be simpler just to place a dedicated tee inline for the air pump instead :)
 

rowan1984

New Member
Joined
17 Nov 2008
Messages
1
In order to spread the flow from a spray bar a litle bit more through out the tank, could I not jsut drill a couple of extra holes. Some firing forwards, some down etc. I know the more holes I have the lower the velocity is but worth a shot?
 

ceg4048

Expert/Global Moderator
Staff member
Joined
11 Jul 2007
Messages
8,993
Location
Chicago, USA
Hi,
While this may seem intuitive, it's actually not worth the shot. The flow pattern created by the series of horizontal jets is circular from back to front, then from front top to front bottom, then from front bottom to rear bottom and then up along the back and then forward again. When you change the hole direction you actually disrupt this pattern as the flow coming straight down is counter to and thus cancels out some of the flow which is on the way up.

Have you ever entertained your little sibling on a swing in the park? At what point in the swings trajectory is it best to push forward? Well, the answer is when the swing has peaked in the aft direction and is on it's way forward again. In that way the energy of your push is in the same direction as the swing's motion, so that the impulse of the forward push, and the forward momentum of the swing combine to be additive. If you want to slow the swing then you push forward while the swing is on its way to back you, i.e. in the opposite directions so that the two energies are subtractive.

Incoherrent and non-uniform flow causes energy dissipation and is counterproductive. Coherrent, uniform flow is additive, causes less turbulence and achieves better energy delivery. This is one of the basic properties of the condition known as "resonance' and this is why, when an army marches across a bridge, they are instructed to avoid marching in unison because hundreds of feet striking the bridge at the same time can actually cause the bridge to collapse due to the simultaneous and synchronous energy input to the structure. :idea:

Cheers,
 

andyh

Member
Joined
1 Jan 2009
Messages
1,924
Location
Derby
Only just found this thread, this is very useful indeed when looking at flow in a tank. Wish i had found it a few weeks ago. Although i am going to make some changes to my tank. :thumbup:
 

hazeljane

Member
Joined
5 Dec 2009
Messages
136
Location
St Helens
Very, Very intresting will look at this in more depth thanks CEG on this you know your onions. :clap: :clap:


Stu.
 

bigmatt

Member
Joined
18 Mar 2010
Messages
676
Location
Castleford, West Yorks.
Hey all,
Thanks for the fascinating thread. As a newcomer to planted tanks i've found it really helpful
I'm redoing my 60x30x30 into a (hopefully) beautiful planted tank, but with a 2yr old at home i'm doing it on the cheap! Having found some cheap clear tubing on eBay
(http://cgi.ebay.co.uk/12mm-x-2mm-Clear- ... 45f182f7d4)
I was going to have a pop at maufacturing my own spray bar and shepherds crook filter intake to aim for that "invisible" look. Following the advice i've read on here my plan is to drill a large number of fairly large diameter holes on one side of the spray bar to achieve the "high turnover/low flow" effect that i think i should be aiming for (please tell me if i'm wrong...!) on my eheim 2234 filter (stated turnover 1000lpm - should be knocking on for 20x turnover if at full belt, but will likely achieve 10x once flow reduction is taken into account). The spray bar will then run as close to full width of the tank as possible sat just below the water line directing flow directly at the front of the tank, with the filter intake then tucked in a corner behind a clump of cabomba.
Does this make sense? Or have i got the wrong end of the stick entirely....??!?!?!?!?!?
Many thanks
Matt
 

ceg4048

Expert/Global Moderator
Staff member
Joined
11 Jul 2007
Messages
8,993
Location
Chicago, USA
Hi Matt,
Yes this is the basically the right idea. You might find it easier though to first experiment with different hole sizes, spacing and tube diameter using cheap PVC tubing first, and then after you settle on a design that works implement it on the clear acrylic. Of course you've got a much smaller tank so your margin for error is wide. In general, from a large tank perspective, I'm more interested in high flow because, like a billiard ball or a racquetball, I need the high kinetic energy to be able to bounce the water from wall to wall. In your case you want to avoid too much velocity and you'll get an immediate drop in velocity simply by extending the bar and adding more holes. But if you drop the velocity too low then you might find that as your plants thicken up and grow in, they start blocking flow in a hurry. An open "Savannah" scape is more forgiving but a thick jungle scape saps the water's energy. As your filter matures it slows the flow as well so you could easily find yourself pining for all that flow you gave up. I'd just start with copying of the Fluval/Eheim cross sectional tube diameter and hole pattern and see how that works, then, bit by bit enlarge the holes to suit your taste if the flow is too violent. :D

Cheers,
 

jcastell

New Member
Joined
1 Apr 2010
Messages
19
This is one of the basic properties of the condition known as "resonance' and this is why, when an army marches across a bridge, they are instructed to avoid marching in unison because hundreds of feet striking the bridge at the same time can actually cause the bridge to collapse due to the simultaneous and synchronous energy input to the structure.

Resonance is to do with harmonics, and therefore not pertinent to the discussion. The incident in question occurred in 1850 when French soldiers crossed a bridge and their uniformed periodic stamping created the resonance that destroyed the bridge, it required a certain frequency and as unfortunate luck would have it, their marching happened to be in the "range". If the bridge was damped differently this would probably not have happened, by why take the risk?

You are seeing a uniform flowing stream as a wave - which it is not. Certain wave makers do produce water waves, and if used incorrectly we can create standing waves leading to stagnant areas.

If you want to create good water flow in the aquarium just use common sense.
 

ceg4048

Expert/Global Moderator
Staff member
Joined
11 Jul 2007
Messages
8,993
Location
Chicago, USA
I think you've misinterpreted my explanation. The concept of resonance is not limited only to harmonics and has much broader applications. If one were to be very technical, the filter's output flow could easily be considered a series of harmonics based on the rotational frequencies and the water pressure pulses each blade of the pump produces. Resonance develops when the frequency of the energy input matches the natural frequency of the system. I was using this concept to develop the idea of being mindful to match flow vectors when combining filter outputs so that the net result is additive and not subtractive. In any case, a stream flows along a linear path where, at any given point in the flow field a unit volume of water does not pass that point more than once. Flow in the tank is non-linear in the sense that it is possible that the unit volume passes a given point multiple times before leaving the tank - where it later returns. This is clearly cyclic and therefore, a harmonic analogy is absolutely appropriate.

jcastell said:
...If you want to create good water flow in the aquarium just use common sense.
Yes, but how is this helpful, and what does this actually mean in practical terms? Clearly, common sense is to perceive flow in the tank in the same way as that in a washing machine which results is collision of streams, wasted energy, stagnation areas and so forth. In this case, it may be more fruitful if common sense is abandoned in favour of the less common analogy associated with harmonics.

Cheers,
 

Similar threads

Top