Fish tank heaters

[1198]

Daft question perhaps,
Ms 1198 and I have a tropical tank. It’s about 500 litres, and by the current maths and thinking in fish world needs a 300W heater. Said heater is heating for, I’d guess 50% max of the time to keep the tank at a lovely temp to keep Nemo and chums content. Fair enough.
We’ve had a few electrical failures recently, where we’ve lost the mains overnight. Obviously this affects the heater and so the temperature.
I’ve got a 600W ac generator, which has been pressed into service for the tank heating. When the heater kicks in the generator coughs a bit, and the small light we’ve had on has massively dimmed.
The question is would I / we be better with a 200 or even 150w heater for this? Yes, it’s be on longer (double the time in the event of a 150w so pretty much permanently on) but would this be a problem?
This would allow the filter and tank light to run through the outage which can’t be a bad thing either, and also would allow the lights in the front room to be on too (stand alone light, not house fitted).
Were it to prove to be a prolonged outage I’d be looking at taking the supply to the fridge / freezer too, obviously waiting until the fish tank was at the top of the temperature band first.
(Am I reading too much into this? Should I just trust the electric will be powered up again before it’s a snag?)

[doggone]

It might be simpler to get a bigger generator that could also run your fridge and other things you want if it's off more than a couple of hours.
600w is unusually puny.

[growler]

also to help with temp chuck a couple of blankets over the tank or even better create a wrap from insulation to put around the tank meaning less power needed to regulate the temp during a power outage
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DILLIGAF

[colink98]

would a 500 litre tank be able to hold its heat for a fairly decent period of time during a power cut.

are the tropical fish not able to handle slight variations in temperature ?
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PCX125 (stolen) - CBF600 (current)
Ride it like you stole it.
ride sensible and not like an idiot and you wont get 6 points in one week.

[MCN]

Don't believe the sticker on the gen. Many small gens say a lot more than they can do.

Half a tonne of water should be able to retain heat for a while. But as suggested above, insulation is your friend. You could ghetto insulate using insulation backed wall board and cut to size. Plate Glass is a shite insulator so adding a layer of heat retaining stuff will pay for its self relatively soon. Even when power is restored.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[1198]

At the risk of reheating (bad pun, sorry!) an old thread I’ve a few updates. I’ve been conducting experiments...
The heater cycles on / off for 2 minutes on, 6 off to keep the water at an desired temp of 24 (temp ranges from 23 to25). If the heater is unplugged, it seems to drop to 23 as before then level out. After an hour it’s still at 23, and if the heater is switched back on again still only takes the usual two minutes to get the water back to the top of the temp band. The filter was left running during this so presumably the water was a reasonably constant temperature throughout the tank, and also the heating in the room remained on. Were it a genuine power cut that would obviously not work and the room would start to cool.
I’m guessing that in future if / when the electric falls over it’s not an immediate panic - no dashing to flash up the smoky old genny!