Natural water flow in a river setup

Nobbley · Post by **Nobbley** » 21 Jun 2003, 13:38

I'd welcome any thoughts / personal experiences on creating a natural water flow in an Amazonian river setup.

Most pumps seem to create a fast but low volume water movement which results in eddys and dead spots where the detritus collects rather than enter the filter. Tunze are producing stream pumps which may be useful but would have to be piped to the opposite end of the tank. Ideally, mechanical filtration would be used in the recirculation line, even if it affects the flow somewhat.

I've been looking at marine "eco" systems and have the following thoughts:

1. Variable, high-volume recirc(s) with mechanical prefilter.
2. Overflow feed into a heavily-planted sump tank with biofilter/ heater etc. fitted in it, 2 return pumps for safety.

Alternatively, I could just add a large external pond filter with output diffuser to go with my Eheim external. My intention is to start with a trial system stocked with Pim. Pictus and see how it goes....

Thanks in advance.

Post by **Silurus** » 21 Jun 2003, 15:16

But the flow in a stream/river in't uniform either. There are also eddy currents and backwaters; the latter is important as it provides habitat heterogeneity so that different species of fishes that otherwise would not be found in the mainstream can be found in the same body of water.

Nobbley · Post by **Nobbley** » 21 Jun 2003, 17:54

Yes, but it's not my intention to totally get rid of eddys or create a diverse community tank. I have digested several articles about river/stream setups (eg. Fishkeeping Answers - Dec'95, Practical Fishkeeping - Xmas '02) and on the P.pictus and wanted something with plenty of steady water flow rather than a swirling pool.

"These catfish thrive in a wide variety of water conditions but seem to be found mainly in well oxygenated rivers with a strong water flow. This is a direct clue to the successful care of Polka Dot catfish in captivity" - Dr.David Sands.

They would, of course, also need areas of calm, plenty of stones, rocks, wood as well as open spaces. Keeping as much of the equipment as possible out of the main tank would also make maintenance easier and less stressful for the fish.

Shane Linder's article on the Natural Catfish Aquarium is very good and informative, I'd like to incorporate some of the techniques/ideas and thought that water flow from one end to the other would be best. Maybe the fish wouldn't know the difference ?

IndefactorX · Post by **IndefactorX** » 21 Jun 2003, 18:39

they have specialty doughnut tanks for this kind of setup, cant give you a price estimate on one tho, but you would have alot more luck with one of those than in a regular tank

Nobbley · Post by **Nobbley** » 22 Jun 2003, 11:33

Very amusing but you are missing the point, let me explain.

Take a river, any river, it could be in south America, Africa or Europe. This river could be a tributary feeding into a larger river or could be the main river itself. Now this river will vary in width and depth as it travels it's course. As the river narrows it will go faster, as it widens it will slow down. This river will support life both in the fastest and slowest speeds and in between.

In most cases, the fish have adapted to live in their surroundings, long/slender fish for fast-flowing open water, sucker mouths for gripping onto stones, short/stocky types in slow moving water. Put the stocky fish in a fast flow and it might not be too happy. Put the slender fish in a still pool and it will probably be Ok, but then the lack of exercise may impact on it's health. You could provide extra aeration but that's only part of it. You may have a dog, you may keep it indoors 24 hours a day and it's fine, but take it for a run and it will be much happier.

So, what I'm suggesting is a tank with an increased flow in a steady manner to suit an active fish type.

Now a river with an average speed at a slow walking pace of 3.6 Km/h will be travelling at 1m/S. If you were to replicate this in your average-sized aquarium with a water depth of 45cm (18") and width 38cm (15") you would need to pump 171 litres of water in 1s. That's 615,600 lph !!

Now in reality you wouldn't want to replicate a real river in such a small body of water. Eheims big hobby 1264 pump is rated at 4,500 lph, that's less than 1%. The problem though is not so much the rate of flow but how it flows into and out of the tank. Directed via a 20mm outlet pipe the flow would be very disruptive, it's exiting the pipe at almost 8 m/s. Yes, the flow will be dispersed as it travels along, but you'd probably get a mini tornado in your tank. Spread the flow across the width and it wouldn't be an issue. Most pumps are designed for high flow through a small outlet, a larger impeller at a slower speed would be bulkier and hence more expensive.

So, my questions are:

Who has tried high-flow "river" systems and what issues did they encounter ?
Any successful or disastrous setups ?
Did the fish appear happy and healthy ?

Thanks to all.

Post by **Silurus** » 22 Jun 2003, 11:41

Did you read the river tank article in loaches.com?

mokmu · Post by **mokmu** » 22 Jun 2003, 16:11

Yes, you can read the article at Loaches.com as Silurus suggested. It will work. I have done that. I can attest to that. But this I will tell you, the bottom line is what silurus also suggested:

"But the flow in a stream/river isn't uniform either. There are also eddy currents and backwaters; the latter is important as it provides habitat heterogeneity so that different species of fishes that otherwise would not be found in the mainstream can be found in the same body of water."

What I understand from your posts is that you want to create a fully uniformed amount of current, much like those testing facilities that swimmers use. This never happens in the wild. It shall always go back to Silurus' suggestion. Even the strongest white water rapids or strongest open water currents will have "tornadoes" or "whirlpools" in different parts of the whole biotope at different times (depending on the weather at that time or the season); some will have smooth flowing areas, some areas won't. There will be slow spots and strong spots in the tank. Detritus will always collect somewhere in the tank (to be honest, this is where you are supposed to do much of your gravel cleaning work).

With that in mind let me give a suggestion. It seems that you want heavy movement of water going from front to back of the tank. You will need a big tank or pond. Combine the loaches.com idea together with an overflow system wherein once water is pushed back, the water flows out of the tank into a sump. You will need a very strong sump pump. This sump pushes the water back into the front end of the tank. You will have a strong current flowing through the tank with the powerheads from the loaches.com idea and extra push from the sump pump. The way I see it this will most probably re-create the swimmers test facility. Now this I've never tried

. It may be too complicated and too big a project. The tank specs may have to be altered to have a lower end-of-tank wall to push water out. The sump will also act as a filter. And to create that over and over again in an unnatural scenario, you'd have to keep that bugger running 24/7 with the water at the same level all the time.

Now that is a crazy idea.

To be honest, I don't think that Mr. Sands has even done what you have suggested. Maybe he's done that in a test facility but looking at all that and some of his books, he hasn't even remotely suggested doing what you are suggesting in a regular display tank.

Regards,
Mike D.

Nobbley · Post by **Nobbley** » 22 Jun 2003, 18:42

Hi Mike,
Many thanks for your comments.

After Silurus posted the loaches.com address I took a look, and yes, this is pretty much what I was hoping to find. It was never my intention to create a fully uniformed amount of current, only as far as was reasonably practicable. Martin's setup used 2 powerheads giving 3,300lph for the recirculation and an external canister for mech/bio filtration. It all looks very good and has been in use for a few years. You could add more or bigger pumps to give greater flow, and use either internal or external arrangements. The recircs could also be sequenced depending on the time of day and when the fish are normally fed. Martin doesn't appear to have used any diffusers on the pump outlets which is something that I thought might be needed.

As far as tank size is concerned, surely the setup could be used in most systems. The smaller the width (front to back) and height (depth) of the tank for a given pump size the faster the water speed, but a big tank would, like you say, be too big a project. I think I'd go for about the same size as Martin, say 5' long x 18" wide x 15 to 18" deep. The length shouldn't really affect the flow, so 4, 5 or 6+ foot long would be much the same.

The sump idea is common in modern reef systems, the main tank stays at a constant level while the sump would change, for example during water changes or with evaporation. A non-siphoning overflow in the main tank takes water to the sump, through the filtration and a pump then pushes it back up to the main tank. Personally, I'd use a drilled tank rather than alter the end wall but either works the same, and like you say, the sump pump would run continuously.

As far as filtration in the sump is concerned, it would be possible to use almost any media you like, a combination perhaps of foam blocks or ceramic, sintered glass and live plants. Using plants with sump lighting which is on when your main tank lights are off and vice versa has been shown to stabilise oxygen and carbon dioxide levels.

So, in summary.....I totally agree and want neither a doughnut aquarium nor a swimmer's test facility !!!!

Many thanks,
Dave.

Any other systems that anyone has come across ?

Post by **Shane** » 22 Jun 2003, 22:55

Dave,
You will find that your riffle tank looks best when it is long and shallow. In my fishroom I have one three shelf rack of tanks that is 81 inches long by 12 inches wide (208cm by 30.5cm). This is perfect because each shelf can hold two 20 longs and a ten or four 10s. I have it set up now with two 20 longs and a ten on the bottom two shelves and four 10s across the top. This gives me ten tanks on one stand consisting of 4 20 longs and six 10s which is pretty nice for species tanks. My thought lately has been to have someone build me a single tank for the top shelf measuring 81 inches long by 12 inches wide and say 11 inches high. I could then set it up as a cut away riffle type tank that would be just under 7 feet long. You might look into having someone make you a special sized tank for the project.
Here is the stand. A local welder made it and delivered it for around US $20.00