Need Heater/thermometer Recommendation

[fanaticbooks]

I have a 28 gal. octagonal fish tank. The top has a narrow opening for the light assembly as well as a hole in the top to hold a heating element.

All I can find for fish tanks are the submersible type heating elements. My problem is, I don't know if they would work for an acrylic octagonal with a small hole in top for the apparatus.

Can anyone advise me? My old one seems to have died.

I keep my house warm so it isn't really needed when I have fish in it, BUT I am having to do a fishless recycle and instructions say get the temp up in the 80's. I need a heater in order to boost it that high.

I will also need something to gauge temperature. I used to have a very nice one that fit on the outside and was pretty accurate. After decades of use it too seems to have gone to thermometer heaven. The newest one for sticking on the side of the tank doesn't seem to register anything. I think it can't work because of the thick acrylic.

Again any advice including brand names would be helpful.
fanaticbooks

edit: just added picture of tank. Hole for thermometer is between light and filter setups on the side next to the phone noted in picture. Hole is about 2" wide, rounded on three sides and segues into square side against wall.

 

[jetajockey]

If you do want a heater I suggest going with a jager. A 100w would probably be fine. I wouldn't bother though if it's just to speed up a fishless cycle or whatever, the extra temp will make it go a little faster but it'll go just fine without it.

As far as thermometers go, I use the $2 glass ones from walmart, they have a suction cup on them and go inside the tank.