Water Evaporation & Heater Keeps Fluctuating

[deansplit]

I have a 33L wall tank (1750x80mm surface area) and I'm roughly losing 1-2L p/week. Is it right to expect this amount of evaporation?

I'm not sure if it's the reason why, but I'm also seeing my digital heater reading fluctuate from 21-28 degrees! It been seen to go from 21-24, up and down within the space of 30 seconds or so, so I mentioned it to the supplier who said it's very accurate so reacts to changes of temp in water current. I find this hard to believe as the current/flow is constant so why would there be a cooler of hotter current all of a sudden? Sometimes the temp is perfect for hours. This morning it's reading 28, the highest ever, yet it's set to 24. The room has underfloor heating ironically, so the temp in the room is more stable than a room with rads – the temp is 21 during the day and 19 during night.

I presume as long as it's within the 'tropical fish temperature' of 21-30 it's ok, as temperature would fluctuate in the wild anyway?

 

[CezzaXV]

The water would fluctuate in the wild, but not to that extent. I'd strongly advise you to invest in a new one because it really shouldn't fluctuate like that.

 

[OldMan47]

I also lose lots of water. My 120 gallon tank requires almost 10 gallons of water each week for evaporation losses. At 1 part in 12, it is almost the same as your losses or maybe even a bit heavier.