[combat1]

OK so bored today and finally got round to fitting two 300w aquarium heaters to my 200 litre storage tank, also got small pump fitted to circulate the water.
The water was very cold to begin with and I set the heaters to around 82deg. after an hour the water was tepid, thought this is good, but after six hours it was still not what you would call warm.
I noticed the lights going out on the heater and for the last couple of hours they were on max, still nowhere near what you would call warm.
How long do they need to be on for? thanks guys.

[MATT BATEMAN (OWC)]

They're aquarium heaters. What would expect, to be able to boil fish?

[andyM]

I think some of these aquarium heaters are not as powerful as they say, particularly the lower powered one's.
I bought a 300 watt heater from a local aquarium shop and was unimpressed with the heat output.
I was surprised to find that on full heat even after a few hours I could hold it in the palm of my hand which suggested to me it doesn't get very hot, and it didn't really make any difference at all to increasing water temperature.
I've since bought a 500 watt aquarium heater from Ebay and it is much more like what I expected.
Water is warm and the heater gets HOT!

[dazmond]

I've tried aquarium heaters before and they just didn't heat the water up at all.2 of em in a 350 tank on all night.they might just stop water from freezing on very cold nights.that's it.

Immersion heater or gas heater if you want hot water mate.

[robert mitchell]

is that 82 farenheit?

can't see an aquarium heater going much higher than 30 c .

[combat1]

Quite correct Robert! At least the heaters worked ok. luckily it only cost me about thirty quid. will have to take up tropical fish.

[Mike #1]

Better heaters and insulate tank , I use a 1kw aquarium heater to heat 300 ltrs without insulation and water gets to about 20 degrees . Mike

[James Bulton]

300 litre tank insulated with a 1 k watt fish tank heater get 33 Degrees over night.

[combat1]

Yes, 1kw immersion seems the way to go. is it safe to plug it into a socket with a rcd or does it need special wiring? Also would my garden 200 litre butt take the heat? Thanks.