For whatever reason, its tough to find a properly sized, fully featured heater for 2-5 gallon nano tanks.
- The hydor flat heaters (7.5 and 15W) have no thermostat and don't really generate enough heat for anything over a gallon or two
- The shortest 25W heater I can find is the VisiTherm original, which is still 6.75" long. This is gargantuan on a relative scale, considering a 200W conventional heater that can heat a 4 foot long 55g tank is only twice as long
- There are a couple waifish 10W and 25W heaters from Tetra and Marineland but they have fixed thermostats (and reviews for the Tetra one at least are terrible)
- The best compromise I'd found until recently is the Catalina 50W titanium heater which has a 5.25" heating element. However its overpowered for a sub-10g tank, leaving little tolerance for any thermostat issues. In addition, its just a nudge too big to fit in an ACMini HOB, which is my intended use.
Anyway, I recently decided I wanted a proper heater (ie one with a reliable thermostat) that was appropriately sized for my Fluval Edge and would also fit into the stock HOB filter.
A few weeks ago, I stumbled upon the Up Aqua line of heaters: link
. These are intended for the Asian market; a quick search on ebay turned up a vendor in Hong Kong. The cost was reasonable; just over $20 shipped, helped by how the Pound has gotten pummelled in recent weeks.
It seemed to fit my specs: 25W (perfect for a 5ish gallon tank); thermostat (remote located to boot) and tiny (4" long heating element). However, it was also 220V, so I'd need a voltage converter.