Thread: New Amalgam UV Lamp

My 40 watt DVS amalgam UV lamp controller has gone from green LED to a red LED
indicating that replacement is due.
which isn't too bad as it has ben running for 3 years.

i looked around for replacement lamps, and the prices seem to vary wildly, from £85 to £39.
so after measuring the lamp i decided to give the £39 from coastal koi a try.
https://coastal-koi.com/product/amal...lacement-bulb/

it is exactly the same dimensions, and pins are the same and fit the holder perfectly.
time will tell if it lasts as long....

Originally Posted by Twhitenosugar

That's where I got my replacement lamp from and has been running well for the last 6 months or so

Sent from my Pixel 8 using Tapatalk

good to know,
less than half the price everywhere else

sounds like koi tax on a standard item from a tap water steriliser.

I'm also about to press the button on another Coastal Koi one.

I notice its listed as 42w instead of the normal 40w, but I guess that shouldn't be a problem.


My current bulb was from Coastal, bought summer 2023 and I'm sure it was listed as a 40w bulb so could well be a different bulb to their current offering.

I only fitted it in May this year after the pond was already starting to discolour, and it took ages to clear, then by end of June the pond was tinted yellow/brown which I thought was the Growth food but this persisted throughout summer.

My bulb is inside the drum, and throughout summer the drum walls had a lot of material / mulm on them whereas they are normally spotless. Again I put it down to the heavier feeding now my temps are supported by the ASHP.

On cleaning the drum last weekend I noticed there is green algae growth inside the drum. Aside from the UV light it is pitch black in there.

The pond never turned completely green at any point, but now its fairly mature (2.5 years) so its difficult to know whether this last Amalgam bulb was doing very much at all.

I'm sure there should not be any green algae growing in the vicinity of a 4 month old amalgam bulb so something isn't right.

Originally Posted by RS2OOO

I'm also about to press the button on another Coastal Koi one.

I notice its listed as 42w instead of the normal 40w, but I guess that shouldn't be a problem.


My current bulb was from Coastal, bought summer 2023 and I'm sure it was listed as a 40w bulb so could well be a different bulb to their current offering.

I only fitted it in May this year after the pond was already starting to discolour, and it took ages to clear, then by end of June the pond was tinted yellow/brown which I thought was the Growth food but this persisted throughout summer.

My bulb is inside the drum, and throughout summer the drum walls had a lot of material / mulm on them whereas they are normally spotless. Again I put it down to the heavier feeding now my temps are supported by the ASHP.

On cleaning the drum last weekend I noticed there is green algae growth inside the drum. Aside from the UV light it is pitch black in there.

The pond never turned completely green at any point, but now its fairly mature (2.5 years) so its difficult to know whether this last Amalgam bulb was doing very much at all.

I'm sure there should not be any green algae growing in the vicinity of a 4 month old amalgam bulb so something isn't right.

sounds like an odd one mate, every tube, flourecent or amalgam, emits UV light if the tube is clear.
as the only difference between UV tubes and normal flourecent lamps is the tri phosphors painted on the inside of the tube that turn the UV light into other wavelengths.
doesn't sound right having algae growing next to it though...

the 42watt is probably a typo, it says 40watt on the drop down box when you order.
I'll check mine see if it says 40w on the tube.

Thinking about it, there's another thing that had me confused with this current amalgam bulb.

I clean the drum waste shoot once a week, and when I lift off the drum lid 100s of little knats fly out. I don't recall seeing that last year and a few times I've wondered how they survive for up to a week under that UV bulb. I would have thought they shouldn't last long at all. The mosquitos that come out don't seem blind either, they find my bare skin with ease!