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Flow question

TarkMalbot

TarkMalbot

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Joined
15 Mar 2013
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172
In my 5 foot long tank I have two external filters one at either end of the tank. I have just been reading about flow and distribution in another topic and was wondering if I would be better off having both suction pipes at one end and both spray bars at the other.

I quote:

"The water must move coherently, i.e., the individual particles of water must all move in the same direction, must meet barriers simultaneously, and must then change direction together to form a smooth even pattern, similar to what you can observe in a stream. If water particles on the left are moving to the right while at the same time, water on the right is moving to the left then their movements tend to cancel each other out and the result is stagnation and an overall net movement of zero"

I have always thought my water wasn't that clear so I am wondering if it is due to the water at the ends of the tank circulating on themselves and the middle of the tank having very little to no flow. Also my heater is in the middle of the tank so not getting any flow either.

Thanks,
Mark.
 
In fact I am answering my own question. I WILL move both suction pipes to one end and both spray bars to the other and then have flow from one end of the tank to the other. Makes perfect sense to do that right?
 
Now and proposed:

tankflow.jpg
 
Hi,
Nice job with the schematics. How did you create the diagrams?

It doesn't really matter that much where you put the intake pipes. What matters most is where the outflow are located and how they are oriented.

Assuming that the spraybar holes are pointed in the horizontal direction (towards the front glass) and not Down towards the bottom, diagram #1 is the typical configuration and I would not change that at all. In fact, if you were to change to the configuration #2 you might encounter more problems because the distance the water must travel (5 feet) is greater and there will be a tendency for the flow to lose energy.

You did not specify the combined filter ratings, but we have often talked about the "10X rule" wherein for most effective flow/distribution, the combined rating of all pumps and filters is the tank volume multiplied by 10. Therefore a 400 liter tank "ideally" requires filter rating of 4000LPH (or thereabouts).

With that strength of flow, configuration#1 becomes highly effective at coherent distribution assuming the spraybar is extended across most of the 5 feet of tank length. If the spraybars are too short then there will be less effectiveness. Using configuration #2 requires a much higher flow rate but can be very effective if the flow rate is high enough.

Here is an example on a 6 foot tank:
8396954239_ff17a4e4ab_z.jpg


Hope this clarifies.

Cheers,
 
Ok thanks. I made the diagrams using microsoft paint. I am not very good with graphics but thought it would give some idea of what I am on about. At the moment it looks something like the photo you sent but the spray bars are not so long:

560095_10151410601639158_204755591_n.jpg


I would say between the two of them the spray bars cover just under half of the length. And flow rate is likely to be an issue as the two pumps are only 1600 lph together. I was told by the LFS that each is suitable for up to 400 liters but I bought two anyway only to do research and find that even two isn't enough. My options would be to buy a third of the same or get rid of the ones I have and buy something different.
 
Hi,
Thanks for the information. I always figured Paint was too cumbersome, but you managed to do a pretty nice job, especially with the arrowheads. I'll have to look at it some more because I'm the worlds worst artist.

In any case, it should be pointed out that LFS don't really know anything about a CO2 injected planted tank. They know a lot about hamsters and frogs I guess, but when it comes to plants they really haven't a clue. My advice is to stop listening to them when they talk about plants. When they talk about frogs they might have some skill.

Filter manufactures also do not have any clue about plants and they do not rate their filters within the context of plants, only within the context of fish, therefore, their recommendations for filter size are meaningless.

If your spraybar only covers half the distance of the tank then you will have solved only half the problem. If yu don't want to spend money on bigger filters then I suggest that you get one or two powerheads such as an appropriately rated Koralia and mount it/them evenly with the spraybar on the other half of the tank. You may still have issues with CO2 depending on how it is being diffused. I really don't like telling people to spend more money after they have already spent a bundle, but if you can afford it then I promise that you will have a much easier go of it with that tank size if you add a another 2000LPH filter. If you chose to go the powerhead route, and if the powerheads are strong enough, then you can mount everything per your diagram #2 because you will now have the muscle to move the water across the length of the tank.

Cheers,
 
Would something like a circulation pump work? I looked up the make you said and found this:

HYDOR KORALIA EVOLUTION 3200 CIRCULATION PUMP

It has 2800 lph circulation? And mount that at the end of my tank and have it set up as diagram 2?

Or even a bigger one with 4000 lph?
 
Two of the smaller pumps would be better than a single one but I feel you may end up just chasing your tail unless you can get a full length spray bar with a decent flow!
However I realise upgrading your power filters is not to be taken lightly & I dont actually think you mentioned having any algae issues ?....so I guess it is worth trying with the circulation pumps.
 
Well at the moment I have no Co2, not many plants and its only been set up less than 2 months. The design of my tank will make it difficult to add any additional pipe work due to the cut outs in the glass lid. I have been looking at external filter options but to get up to 4000 litres per hour seems a massive and expensive task so a circulation pump is looking favourable at the moment.
 
I am turning my smaller tank into a high tech setup first so this one may happen one day. I will see how it goes.
 
Hi,
As foxfish mentions, the 10X rule, as well as the paragraph you quoted applies strictly to CO2 enriched tanks only. I apologize for assuming that the tank was CO2 enriched. There really is no need to spend more money if the tank is non-CO2 enriched and if you are not having any problems.

Cheers,
 
The funny thing is that since getting my new 5 foot tank I have been spending all my money and efforts in my old tank that my wife is turning into a planted tank. Once I have that up and running and can maintain a smaller 165 litre tanks I may then turn more attention to the big tank.

So to conclude I might as well just keep the tank as it is set up now as in diagram 1?
 
How does joining two spray bars together to double their length affect the efficiency of the pump and the flow? From an engineering point of view I would imagine having more holes from the added spray bar would mean less pressure out of each hole but less restrictive to the pump alling a higher turnover?
 
Well I dont actually know of a set formula for hole sizing & placing but, I have successfully built dozens of spray bars over the years.
Quite easy & cheap to diy a pvc spray bar & you can then use that as a template to build an acrylic one if you want.
I would still use two pipes though or use an obstruction in the middle of a single pipe, most folk join two half lengths together if you are useing independent pumps.
Just bear in mind there are very different criteria required for high & low tech tanks & although good even flow is important in a low tech you just dont need very much of it!
 
Thanks for the advice. I was thinking of asking Maidenhead Aquatics if they could get hold of the spray bars for my filters and then just taking the plug out of end and extending them somehow. Then I would have spray bar pretty much the whole way across the back of the tank as shown by ceg.
 
ceg4048 said:
If you chose to go the powerhead route, and if the powerheads are strong enough, then you can mount everything per your diagram #2 because you will now have the muscle to move the water across the length of the tank.

Cheers,
Click to expand...

I went for this option. 1600 filtered external pumps and 3200 Hydor Powerhead.

74391FD5-17FA-476B-9542-3A1CE0EFAC65-436-000001018C2F1696.jpg


I have one spray bar pointing horizontally just below the surface without much surface agitation, one scrap bar pointing at about 70 degrees downwards and the powerhead pointing about 30 degrees through the tank.

The fish like swimming against the current like its some sort of fair ground ride!
 
Hi mate,
Yeah, give that a try and see what works. Don't get locked into any one particular solution. Look closely at the movement of bubbles and other small, light pieces of debris and see what the pattern of movement is. Ultimately the plant growth and health performance will indicate the validity of the configuration.

Cheers,
 
The top half if the water seems to be flowing away from the spray bars and pump and then the bottom half of the water flowing in the opposite direction. I am hoping this means the pumps are strong enough to force the water along the tank and its hitting the end and then being sucked back along the bottom.
 
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