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URGENT - Please Help with Electrical Inline Water Heater with Temperature Controller

Hi everyone!

I am a koi hobbyist living in Montreal, Canada. I have an 8000 gallon outdoor pond in which I have 24 koi, ranging in size from 12" to 24". I could or should I say "should" leave them outside for the winter, but I've opted to bring them inside now for many years. I used to have 3000 gallons in my basement winter set up, split between two tanks. One, which was a 1700 gallon above ground pool developed several leaks over the years, so I trashed it last summer leaving me with the one tank, a 1200 gallon capacity. Needless to say, this year fish are very stressed due to being overcrowded. I could give you plenty of more details as to how I care for them,may need for a hospital tank, but I'd rather get straight to my question. :)

Two fish have developed two small ulcers which I am currently treating, but I need to raise the water temperature from its current 60 degrees F to 76-77 degrees F.

I'm on a restricted budget (unemployed), so I am not in the position to purchase an expensive inline spa water heater or anything else in the same price range.

I've attached a couple of videos of DIY inline heaters, easy to make for under $100., but need to know what supplies I would need to change up if going with a higher watt system. I would like to use either a 1500 or possibly 2000 watt element. I'm assuming that the first video below is a 1000 watt or less, because nowhere is wattaged mentioned (unless I missed it). Second video is well under 1000 watts.

So if any of you have experience with these type of DIY devices, kindly advise the correct parts required, meaning: element, size of thermostat controller and If I need a solid state relay? The relay part has me confused as I have never used one in any electrical application. Remember, this is for a 110 outlet, which already has a 1/4 horsepower pump and a hefty air pump plugged in to. What amps should I have on this circuit? (maybe I need to call a licensed electrician to increase amps at my electrical box?)

So here are the a couple links for the general idea.
Please answer ASAP as my two sick fish need more warmth in order to heal.


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Sorry Pieter for the mixup and thanks for all the handy info and chart!

I'm feeling pretty deflated right now. I was told on a few koi forums that a 1500 watt element should do he trick indoors, but would take a number of hours to first establish desired heat.

The reason I am doing all this "DIY" is due to the fact that I am unemployed at the moment and don't have the financial resources to be spending a lot. I have lots of health issues going on at the moment and to be honest am in no position both financially and physically to be rerouting wiring through ceilings and such. Just touched cord and it's cold, so should I just keep what I have? I don't own a volt meter, but is it possible the I have the polarity wrong???

According to Pieter's chart above, isn't it feasible that a 1500 watt element will work?

I'm so stressed out over this that I've been poppin' Xanax like candy....

If there's no hope that a 1500 watt element will work, I need to know ASAP as all my fish treatments with medication will have been for nothing.

Anyway, gotta run. Have an appointment I need to get ready for. Hopefully there will be some good info before I leave the house.

All the research I am aware of seems to agree with a rule of thumb of 3 to 5 watts per gallon being required to heat a system with enough flexibility to not stress the fish. The more exposure to the outside extreme temperatures the closer to 5 watts per gallon. The warmer the climate the closer to the 3 watt range a design can be planned. 

Thanks Glenn for info above!

Steve, Pieter, Glenn or anyone! ( :))

So, how many watts additional do I need? My 1200 gallon tank is in a separate unfinished room in my basement - temperature varies depending on weather outside as one wall in my fish room is a common wall shared with my garage, but fish room ambient air is always between 68 and 70 degrees F. Temperature in garage is a steady 41 degrees F. I do have a baseboard heater in the fish room that I could crank a little more, but to be honest, it seems to be running all the time when set at 70 degrees F.

Okay, so I guess I need to order another stainless steel element which here in Canada is $52. plus tax and shipping, so looking at $70. The bulkhead with tax and shipping was close to $25. Do I also need to purchase all ingredients for a second control box? Can someone chime in on this?

If I use Glenn's recipe from above and use 3.5 watts as an average, it translates to 4200 watts, so does this mean I need three 1500 watt elements installed?????

Please know that I truly appreciate all the input from each and everyone of you, but I need to resolve this in an economical way without delay... Hope you understand the urgency (sick fish).

Glenn said:

All the research I am aware of seems to agree with a rule of thumb of 3 to 5 watts per gallon being required to heat a system with enough flexibility to not stress the fish. The more exposure to the outside extreme temperatures the closer to 5 watts per gallon. The warmer the climate the closer to the 3 watt range a design can be planned. 

Can I call you after 8?
The least I can do is call you... I have your number from the other night on file. Let me know if it's the one I can reach you after 8?

Cheer up! the glass is half full. Any system needs some tweaking/set up.

Suggest that you borrow/invest in some measurement equipment - such as multi-meter ~ 10USD - should be available at any hardware store.

You can test the heater by heating a small volume of water and compare to kettle

- Recently a member of this forum traced his problems to a faulty heater element - (it was new).

With your ~40A SSR you should be able to drive  3 elements x 1500W /120V -> 37.5A - I just don't know what your house supply can handle - and the electricity bill. This will take 11 hr's to get from 15degC to 25degC (loss less)

The enjoyment received from activities such as these sometimes need to offer the only profit.

Sorry I haven't followed this conversation too well from the start or I would have a better idea of your over all set up. But from what I do know so far, I think the best thing to do if possible might be to "partition" your fish into a smaller area requiring less energy. If for instance you could fashion some sort of portioning wall or barrel within the fish way, you might be in a better situation to "over-winter in 500-1000 or less gallons that need be heated.

I think rather than throwing more money at the problem, more options should be explored. There are after all, more ways than one to skin a fish.

Today was a better day... I was just due for a meltdown... Lol.

Anyway, I'm in the process of adding more heat to the room. Current baseboard was/is undersized for space. Will also be covering the tank with heavy duty clear plastic to retain and prevent heat loss. Purchased a volt meter... Need to check out YouTube for use.

Update and a question:

I've now covered my 1200 gallon fish tank with a plastic tarpaulin to retain heat from inline heater.

Prior to adding the inline heating element, water temperature usually lagged behind room temperature by 4 or 5 degrees (water 65F. and air 70F.).

After adding the inline heater, temperature over the next day or two only climbed a meager 3 degrees... So, with your help and direction, I've added an additional 1500 watt space heater. I plugged space heater in this morning and within a short period, room temperature that had been stuck between 68 - 70F. quickly jumped to 75F. and is still climbing.

So here's my question. Water temperature under tarpaulin is sitting at a very steady 70F. Should I peel back some of the tarp to allow the now warmer air temps to aid warming of water or should I keep the tank completely covered? Please note, between my wood frame and liner I have styrofoam insulation, so wouldn't this keep the room temperature out?

Please share your thoughts... I know we're almost at the finish line!


I would be speculating either way. Logic says uncover and air will warm surface, but evaporation causes evaporative cooling.  Not sure which would win.  Try covered for 24 hrs and then uncover and see

Yes, a conundrum... I'll post results tomorrow.

Thanks Steve!
Do you have styrofoam insulation between floor and FT?

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