Cupro-Nickel - Ist it safe?

[Arthur]

A Teledyne-Laars dealer recently said that their standard pool heaters now come with a cupro-nickel heat exchanger and therefore are safe for heating koi ponds without any modification.

I did some research on cupro-nickel and it appears to be a very interesting alloy but nowwhere I found spoke about fish safety.

[Russell Peters]

Yes, They are safe, but I will tell you I have had a heater with a copper unit on my pond at home for 5 years and no signs of copper in the water. Do as you will.

[johnsmith]

yes, safER. It is a harder alloy. Less prone to leeching. Interesting tidbit on copper and pH. In my old pond, I run water right from the well. The pH out of the ground water is low- very low ( 5.5). This is due to carbon dioxide trapped in the ground water. Once up. exposed to the air, the pH rises to a natural 7.2. I was away at the beach house for three weeks and the water was shut off to the old pond. The new pond gets water from a neutralizer and water softener and is on an auto timer and auto refill.
When I got home I did a water change in the old pond after letting the water run for ten minutes to drain water from the copper lines. After the water change I noticed the fish in that pond sulking- you guessed it- copper! leeching from copper pipe exposed to that low acid pH. I did another water change with a resin filter all this time and the white resiin foam turned bright blue after 1000 gallons! I bound the rest in the pond with an additive and the fish began feeding within ten minutes- the cahage in behavior was profound!
Koi keeping will keep you humble. JR

[Moneypit]

I would not trust it in my pond, as JR said leaching copper and other metals depends largly on PH, if it were me I would stick to Stainless Steal.

[johnsmith]

well that IS the ultimate answer - stainless steel. But the tranfer chacteristicsof SS are not as good as copper or 'blended' copper alloy. Honestly, I traded my spa heater ( rayband) in for a heat exchanger. There, stainless is wrapped so that all transferred heat can only go to the passing pond water. If you lean over a swimming pool heater or a spa heater you can feel the lost 'dollars' rising into your face!
I've also used the heat exchangers with coils- you can get the plastic piping and the transfer is also pretty good as the inside is copper. But here the copper is totally isolated from the pond water. I use these coils ( winding like wrapped garden hose) in the base of my trickle towers- works great for the fish and the bacteria in the TT column! JR

[PapaBear]

Copper alloys are not all created equal. Most folks like us can only get refrigeration grade or standard water grade, and they do leach differently. I would think the Curpo Nickel would be safe and effective, but there should be an MSDS avialable for detailed info.
Another often overlooked alternative is SS beverage tubing. It is very thin walled, has excellent heat exchange properties compared to standard SS, is highly acid resistant alloy material (food grade) and it is sold in COILS rather than sticks (great for heat exchangers ). It has been a while since I bought any, but it is comparably priced to standard copper and has a burst strength of around 1000psi.

[johnsmith]

Larry, I'll take a picture of the coil I'm using and post it tonight. JR

[Arthur]

So my suspitions were justified: under acid condition cupro-nickel will release copper in the water (somewhat less than copper alone). Given the very low copper tolerance of koi, I would say that it is better to use SS or Cadmium coated heat exchangers.

Thanks again

[Moneypit]

Or if you are doing a new pond with a concrete bottom you could just do this and not have to worry about contaminating the pond water at all