Just had to replace my Aquael Comfort Zone heater as it was maintaining the water temperature exactly 2 degrees above the setting. Made an emergency trip to Pets At Home and bought a Interpet Delta Therm, which is working well, however I've noticed a small amount of condensation inside the glass tube. Interpet's webite says this is perfectly normal and not a safety issue, apparently it is caused by high humidity in the factory. I'm still a little concerned though. Is this really OK? If not, can anyone recommend decent brand of heater? Wouldn't get another Aquael, it worked reasonably well until the thermostat started playing up, but I wasn't entirely happy with the build quality.

No idea about the safety of the thermometer you have but I love the rena smart heaters. They have some really nice features like buffering the temperature so it never drops too fast. TBH I much prefer the silicone heaters to the glass ones anyway but the smart heaters are particularly nice

If you have an external filter I've heard good things about the Hydor Inline ones- its one less piece of equipment in the tank, which is often nice.

Thanks for the replies. The Hydor Inline heaters do seem to be highly recommended, unfortunately I have an internal filter so that won't be an option. Rena Smart Heaters - these do sound good, but having just done a little research they do seem to have a bit of a reputation for going wrong after a couple of months. I have absolutely no experience of anything other than glass heaters tbh I hadn't realised there was any other type of internal heater. The Interpet glass ones get mixed reviews. This one does seem to be working well at the moment but as I said the condensation does worry me a little, despite what Interpet's website says.

When you are rich and upgrade tank and filter, get an eheim thermofilter - heating element is inside the external filter so nothing in tank to get in the way or break, and it keeps the temperature rock steady

I'm not intending to upgrade the tank/filter any time soon. Not meaning to be rude but I need advice on what I should do now, not what to do several years down the line. Firstly, is my existing heater safe? Secondly, if it isn't safe, what one should I get?

Heaters are all are rather similar really unless you start opting for the thermofilters etc (on my wish list)

I've used the Juwel filters initially that came with all the tanks I had (very good/safe but upgraded to the next size up as for some reason they tend to supply the next size down )

Now, having just the one tank, I'm using the Delta Therm like you, very accurate and this one has been going for a number of years. There is a little bit of condensation in the tube (just checked after letting it cool for 10 mins first) but it's been a good buy and no issues so far.

Personally, I'd stick with it for now if it is doing it'sjob. I like mine.

Thanks Violet, as I said Interpet's website says it's fine, but I don't necessarily trust that as they're trying to sell it after all, just needed someone to confirm either way and put my mind at ease. I've still got the old Aquael one as a backup just in case something goes wrong, although the thermostat's faulty it still heats the water, so it'll be fine for an emergency. For all I know that one may have condensation too but the glass has a frosted finish so it's impossible to see.