Getting The Flow Right

[ellena]

So I have this betta tank, approx 30cm cube. I had a 25w heater in there. Set to 32C, it was about 26 and only 21 at the bottom.
So I bought a 100w heater. Set to 28 it was 28 at the top, but still 21 at the bottom. Set to 30 it was 30 at the top, still 21 at the bottom.
When I say 'top' I mean with a regular aquarium therm, so actually a few inches from the top.
The heater is about 30cm long, so set diagonally across the whole back of the tank. The filter is a fluval mini and is over the hot end of the heater. The flow is reduced for the betta by pulling the 2 sections of the filter apart slightly. I have kept an eye on stats with this arrangement and it seems to handle the waste fine
I think the problem might be the filter is sucking in all the hot water and taking it to the top of the tank where it just hangs about as the filter outlet doesn't really 'fire' it very far. And naturally the hot water will stay at the top.
Do you think it would help if I moved the filter to the other side, next to the higher, cold end of the heater?
Or, any other ideas? I can't believe a 100w heater can't keep a 5 gall tank warm!

 

[mattlee]

try aiming the filter flow at the heater, this will push the heat around the tank more as it will be picked up in the flow

 

[ellena]

The filter doesn't have a directable outlet and with the tank being so small, there's very little room for manoeuvre. Thanks for the suggestion though