Whats going on? its cooking in here

[mincedgreen]

Hiya!,

I'm new to this forum but I've been reading it for a while

I have a 170L tank with an internal filter, and a 200w heater. Its currently got about 15ish platies in it, which came from my pond outdoors. So, they're pretty used to the cold. I'm running a heater in the tank as its making the house too cold without it!

my question is: my heater seems to be cooking my fish. I set it last night to 22 degrees, and when I got up this morning the tank thermometer showed the tank was at 26 degrees, but the heater still hadn't turned itself off. I assumed the themostat was naffed and turned the heater off (it was secondhand). Today I went a got a new heater (200w Visi-Therm), and set it to 26 degrees when I put it in the tank as I didn't want to drop the temperature to fast and shock the fish. 2 hours later and the tank is at 28 degrees, heater still churning away. Turned the heater down to 22 degrees and the thermostat turned it off.

Whats going on? Is the internal filter kicking out enough heat that I don't need the heater running at all?

[smidey]

That sounds pretty odd, no mater what is heating the water the heater should turn off when it is at the set temp. have you got another thermometer to check if the one you have in the tank is correct? i have jager heaters which keep the tank within 1 degree of what it's set at & when i have the fire going they don't stay on to heat the tank.

[Cricketman]

Your probably right that the original was naff-ed.

if your heater didn't need to be on it wouldn't be on, the temperature difference between the inlet and outlet of your pump is minimal, and since the size tank your talking about is relatively small, the heat holding is lower than a bigger tank. therefore running without a heater is not going to be feasible.

2 possible reasons for your difference in readings.

1) your heater indicator is inaccurate, try setting it to a slightly lower temperature, 26 or so? and see how that goes.

2) your thermometer that you are using is inaccurate. digital thermometers and stick on variety are notorious for failing. personally (and from many professionals) I only use glass in-tank thermometers.

hope that helps.

[Ira]

First of all, don't use the temperature scale on the side of the heater thinking that if it says 22° on the heater it will keep the tank at 22°. The scale on the heater is a LIE.

If the tank is too hot turn the heater down. If it's too cold turn it up.

[Sunbird73]

I am not a seasoned expert like some here but in my limited experience the thermostat on heaters is not exactly accurate ( I am guessing this may be different for different brands) and you need to adjust it to get it maintaining the right temperature for your tank.

For example, in my little (22L) tank, if I set the heater to 20 degrees it maintains the tank at 24 degrees. If I set it to 22 degrees it maintains it at 28 degrees. I think this is because the light on the tank contributes to the temperature of the water as well as the heater.

Similarly the other heaters in the bigger tanks settings are slightly different to the *actual* temperatures of the tank. I have also discovered that the type of thermometer you use can alter things too - I have two cheap mercury-type ones that read 2 whole degrees different to each other for the same position in the tank (I checked them side by side). Because of this I switched to a digital one, which seems more accurate.

So it may just be you need to adjust your heater down a little to get the temp you want. (obviously an ideal situation would have been to check the working of the heater without fish in the tank).

[smidey]

First of all, don't use the temperature scale on the side of the heater thinking that if it says 22° on the heater it will keep the tank at 22°. The scale on the heater is a LIE.

is that the case for these visi therms? my jagers are perfectly accurate, dial 27 & thats what you get.

[Ira]

is that the case for these visi therms? my jagers are perfectly accurate, dial 27 & thats what you get.

None of my jagers are accurate, but the visitherms are the worst for it. I don't have any running now to check but I remember them being in the region of +-4 degrees off.

[phoenix44]

to recalibrate a jager, yank up the little blue button like thing; take a temp reading and set the dial to that temp and then push the button down again. presto. your jager is now accurate.

make sure the heater pilot light is off when you do this - if it's on it means it is still heating and this will result in an incorrect calibration.

[BikBok]

My jager heater has always been spot on - i'm very impressed after having used the not as accurate aqua ones previously. And I like the calibration dial.

[smidey]

None of my jagers are accurate,

how far off are they?

[Ira]

how far off are they?

Dunno, I'd have to check, a couple I think.

[smidey]

all 3 of mine are spot on.

[mac]

Mine are all spot on. Some of them are normally out by 2' for safety of the fish.

Was the light on the heater always on? Or just was it on when you looked at it. Because it may have just turned on.

[mincedgreen]

Well I put a glass themometer in there which showed how wildly innacurate the stick on one is! wow. The tank is at 22 degrees and the heater (set to 22 degrees), is coping beautifully at keeping it there. All fish are A-Ok.

Crisis averted Thanks Guys!