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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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Hi Chris,

I watched the video and hear where he says they aren't rated for that current.   Some have  a 10 amp rating, some have a 30 amp rating.  You would just need to verify what you purchase.  It is an asian made box that is often duplicated.  

You can always add a relay inline for safety, if you are unsure or order the wrong item. 

This is what I ordered.... Does it seem right?


I have pics posted on the "Community Home " " photos" screen. and on my home page. I cant seem to get them to load on this thread with the proper orientation. If you cant get to them through my user page let me know and I will try to get them on here somehow.

Hi Chris

I see your SSR has DC input (these are usually low ~ 3Vdc - I can't make out clear what type SSR you use)

- maybe ask your supplier for a Relay with 120Vac coil? 

else you need some additional electronics to rectify AC to DC- or separate psu.

The 40 Amps seems a bit high - if you're wall socket can deliver 20 A (GFI protected/rated) - but it won't kill your equipment - maybe just your pocket. To determine current require for a heater relay - divide heater power (2000W) by line voltage (120V) -> 16amps - so 25A/120Vac relay should do. such as opto120A25 or similar

To summarize - you need to specify your input coil - 120Vac is an industry standard as well as current capacity and break voltage on the contacts i.e.  and

(Note difference between part number xxDxx and xxAxx - easily to take wrong one)

You can then connect your SSR input/coil in serie with the controller controller relay.

Controller -

According to the specification the output relay can only handle 10A - I'm not sure what model you've bought - so an external relay will be required to control current higher than 10A,

UPC CODE:0848454020553

Technical Parameters:
1. Temperature measuring range: -50°~99°C;
2. Resolution: 0.1°C;
3. Accuracy: ±1°C (-50~70°C);
4. Sensor error delay: 1 minute
5. Power supply: 110VAC±10%, 50/60Hz;
6. Power consumption: less than 3W;
7. Sensor: NTC sensor (1PC);

8. Relay contact capacity: Cool 10A/250VAC;Heat 10A/250VAC;


Would be interested on time taken to heat your system - according to my simple heater model - no heat losses - it will take a 2000W heater 35hr to heat from 60°F(15°C) to 77°f(25°C) - so you'll probably require added heating and/or isolation - not sure what temperature swings you'll experience as it's in your basements and once heated probably will stay more even..  Also not sure how fast the water mix as to not stress fish further by temperature gradient. The temperature controller has very nice resolution and accuracy - so you can keep temperature nearly constant - if your heater(-s) can keep up.

Any other more economical methods you can think to heat (wood/gas/etc?)

Note I'm not resident in USA and not knowledgeable re wiring standards there.

Morning Chris, 

Sorry, I was away from my pc yesterday.  As Pieter noted above, looking at the relay info, there would be an issue with the control voltage.  I sketched out a simple way you can get all these parts to work.  That relay only needs a bit of power to open or close.  So here is basically the way it will work.  Power from the wall needs to to to power the STC-1000 controller. 
I would take an old pc cord or extention cord and cut the end off and wire it to the STC-1000.  Left two leads.  Connect ground if you can too.

Then you plug this into the wall.  It will just energize the controller.  

From there, the thermostat sensor leads connect to the STC and go into the tank water.

Then find a wall wart (Ac to Dc transformer) that you have laying around that gives you DC output somewhere in the range between 3-36 Vdc. I would shoot for 12 v.   Try to find a good size one that may produce 500 ma or 1 amp just to have durability over time.

This DC power source will then have a red + and Black - lead coming out the wall wart.  Take the + to the Heater contact on the STC-1000 and then take another wire from second connector of heater contact StC and run this to one side of the SSR control.   Then from the other side of the SSR control connect the - black wire from wall wart.

This  will make up your switched low voltage control circuit.  

Now Get a quality extention cord that can carry the load of your heater.  With GROUND.  Connect this wire from GFCI plug to SSR.  (The NO normally open) Side of the load side of the SSR will interupt the BLACK wire on this extention cord.  From there both black and white wires will continue on to the Heater element.

Think about this in pieces and it is easier.  The heater with the relay in the black line as one piece.

The 12 vdc going from transformer to STC control relay to High Current SSR as another system

and STC-100 with its own power cord for a central brain as another.   
Another benefit with this all will be when you decide to reuse the STC for another task or project later, it is not hard to reconfigure.  

I would recommend that you also make sure that the Ground from the GFCI is connected to the water in the tank some how.  You say you have a 1200 gal tank, if this is metal, then just go to the top rim where there is no water on other side and sand a clean spot.  Drill a hole and connect the wire with a small bolt.  Put silicone around top to keep from corroding over time.  This will bond the ground from the electrical system to the tank frame.  This way if anything goes wrong, the power that hits the water then gets drained through this wire into the ground system in your home electrical system.  You may be well served to do this with a dedicated single ground wire that is ALWAYS connected.  If it is part of the electric element power supply it is safe while the element is plugged in.  If you unplug it when not in use etc, and something else begins to fail, water pump, etc then the ground would be disconnected too.   

It may be worth mentioning that if you have a steel tank then it is likely electrically grounded by physically touching the ground, but trace voltage in a wet environment isn't worth risking.  Grounding is very VERY important.  Heater elements can and do get small cracks in them that let small amounts of electricity into the water.  This will trip a GFCI breaker.  This is why hot tubs are required to have them now.  I may be giving you too much, but I would rather go over than under with regard to electric and safety.  

If you get stumped, snap a pic or two and upload it.  

Is canadian exchange rate really 2-1 from us right now???

Steve and Pieter,

First off, let me thank both of you (and all) for the time spent in helping me! And Steve, thanks for the time spent on your diagram... Makes things a little easier, but before I get there I need to get my "parts required" list in order.

Anyway, looks like I ordered the wrong ssr. Here is the link to the primary video that this idea is from.

In the video, in the author's comments section, he has a link for the ssr.... Is this the one I should have purchased for my set up???? Please keep in mind that I already have a water pump, air pump on the same circuit. Here are the water pump and air pump specs. (pump 1/8 HP 115 VAC) and (air 120 VAC - 60 HZ).

Here's the suggested ssr link from video:

Just as a reminder, the threaded heating element is going directly through the side wall of my standard size sand pool filter via a threaded bulkhead, far above the sand line, but well below the water line. The tank is made from Fiberglass.

I cannot ground my fish tank as mentioned. It's a wood build with EPDM liner, but I do have a stainless steel sink close to the filter... Could this help... or am I just setting myself up for shake 'n Bake?

Steve, you mention adding a wall wart... Not sure exactly what that is, but if I need it, could you google the correct size on Amazon or somewhere so I know what to look for and post the link here?

I'm still having the darnedest time finding a stainless / incoloy 120v 1500 watt element here in Canada. I've made plenty of email inquires across Canada and if I come up empty handed today, I will drive to New York State this weekend to shop there....

Our Canadian dollar at the Bank of Canada this morning is valued at 72 cents U.S. - but when I order stuff online from the U.S. The rate is even worse, then there's Customs' fees, and UPS paperwork fees, so cheaper if I just make the 4 hour return car drive :(.

Guess the final two things I need before I get started are, verification and links to exact ssr required and the wall wart thingamajig?

Thanks again guys - have a great day! I'll be anxiously awaiting a response...


Hi Chris,

You are more than welcome.

The item the youtube build recommends is a contactor.  Similar in many ways to what you have purchased.  No worry with what you have purchased. 

Since you have a wooden tank, I would recommend just ensuring that your recirculating pump is correctly grounded.  It likely has a fairly substantial metal housing, will be used all the time and should have a ground already.  This will suffice.

A "Wall Wart" is a slang term for the little black box that you plug into the wall to power little electronics. It is an AC to DC transformer.  Most people have them laying around from misc broken things.  for example an old toy, rechargable battery or tool, old laptop computer power cord/supply.  Basicly you need a way to get a DC current to run the SSR you purchased. Google "Wall Wart" and you will see what I mean.  

I have read that Stainless elements are best, but with difficulty finding what you need, I don't know if they are really essential.  The standard element would work just fine, I am not sure if there would be some risk to the fish?? May be worth further research there.  Personally, I would purchase the same item used and stocked for water heater.

They are zinc coated and have copper elements.  $11 us. 

You may reach out directly with one of the moderators on this site to ask if they can give you a straight up answer (Based on fact not theory) on if there is any risk in using one element vs another. 

Pentair is a supplier in FL that carries products for commercial aquaponics and aquariums.  They sell replacement elements for systems they sell for this purpose and they are Copper / Nickle elements.  Same as what your local hardware store sells you for your electric water heater.

Steve, Thanks for getting back in lightning speed!! I'll check out your links, but I know for a fact that it is said that any continuous flow use with an element other than stainless or incoloy could be harmful to koi, so I'd rather be safe than sorry.

The wall wart thing... Think I have a few kicking around in my electrical junk box... So I'll take a look and post back what I have found.

Thanks again!
Steve, Just got off the phone with Pentair customer service. Apparently if element is in an isolated water tank then anything goes, but for inline freshwater it needs to be stainless or titanium - saltwater, only titanium.

Makin' some coffee now, will look for wall wart thing soon.
Here is one that you can't read from photo. It is rated as follows! But I don't think this one is suited for what you are asking for?

Alter Lansing class 2 power unit
Input AC 120v 60 Hz 0.6A
Output AC 13.0v 4A 52va
Here's another one.
And lastly the one that may work?

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