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Heat Sink.........Coolwater River-Tank conflict.

Posted By: Martin Thoene <martin.thoene@lakenheath.af.mil>
Date: Saturday, 13 November 1999, at 2:37 a.m.

When I set up my second River-Tank, intending it for some of the cooler water Loaches available, I installed the second-hand heater that came with all the rest of the second-hand tank & equipment. The next day the tank temp was off the scale (88+). I turned it down to the minimum, but that made no difference. I X'd the obviously faulty thing and the tank now runs without a heater.

It's been fluctuating with ambient room temperature since, but rarely drops below 72F. On Tuesday I received the 2 Aquaclear 402 Powerheads to run the water manifold. Now the tank is running at a constant 78 degrees, so is hardly cool water any more. The Botia superciliaris, pulchra, and the 4 Nemachelius sp. are quite happy, despite being able to live in much cooler conditions.

Fish are pretty adaptable sometimes........the superciliaris was in the tank when it overheated.

Any powered pumping device for Aquaria will produce heat as a by-product of the electric motor. This is why you shouldn't use most Powerheads out of water. They rely on being immersed for cooling. Heat is lost to the water. This is normally not a problem with the averagely powered tank using maybe one Powerhead sized as per manufacturer's recommendations to the tank. The problem comes when you go outside the normal flow levels by oversizing and multiplying the numbers of Powerheads to give the effect in my River-Tank design. I also have a Fluval 303 External Cannister Filter running on the tank, which may contribute some heat, although as the motor casing is on top of the filter and exposed to the air it's effect may not be so significant.

The equipment is producing more than a "normal" level of heat and therefore has a significant affect upon the tank temperature. In my case it's an acceptable level that means I can keep regular "tropicals" in the tank without a heater, but also means I have no thermostatic control over the temperature. Maybe if the ambient room temp was lower the tank would be too, but with the central heating on during the day, I only see about a degree lower difference when it's not on at night. As I've only just set this up I can't comment on the effect during Summer temperatures, but last Summer my Lounge was hotter than my Clown tank which is maintained at 86F!

In England these high Summer temps are not as common as the temps in the 'States are, so I could maybe see a problem arising running a River-Tank system in the US if you were trying to specifically keep cooler water fishes. Even regular Tropicals could have a problem with the amount of heat being produced.

I know that Marine fishkeepers have already found this to be a problem. They use big powerheads to create currents and surges within their tanks, and combined with Metal Halide lighting the temperatures may soar to unnaceptable levels. Some have fitted very expensive coolers to the tanks in order to control the temperatures.

Things aren't that bad with mine, thankfully, and I guess that one thing that's good is I'm getting the water movement I required, plus I don't have to pay any electricity bill for heating the tank as it's now a by-product of the water-flow production.

How MUCH heat any given unit produces is probably dependant on it's wattage and certain design details, so I'm sure 2 different manufacturer's models of identical wattage may produce slightly different amounts of heat. The size of tank will effect the heat effect produced, plus the surroundings, insulation and ambient air temperature will be variables.

I'd be really interested to know if other's have noticed this effect, and anyone who's contemplating or built a high-flow set-up should maybe take this into consideration when sizing the pumps. Overpowereing the system may result in too much heat-sink from the pumps producing unnaceptable heat levels in the tank.

I calculated that this tank turns over about 18 times per hour as against 16 for my first River-Tank. I may swich off the RT1 heater for a day and see what temp that tank runs at. It currently runs about 75 degrees and I'd like to know if the Powerheads are making that heat or the heater.

Because my River-Tank design is a relatively new concept, I've no data to go on regarding this heat problem, so can't recommend specific Powerhead/tank size combos. I'd very much appreciate some feed back from others on this as a few of you seem to be getting into this idea. With more experience of these sorts of set-ups we could amass enough data to give others do's and don'ts regarding pump sizing. My limited experience so far seems to point to about 17 times an hour turnover being a reasonable fig