I would read about the brand American Aquarium recommends. Most of the brands out there do not do a decent job. The flow rates needed for UV and filtration are completely different. Nor do I use filters with built in heaters. If for no other reason than I want to fill my filters with media not other equipment than can be placed elsewhere. Any tank where I have a canister I use an inline heater just to keep one more ugly piece of equipment out of the tank and never in the filter.
Incidentally, I have used a big variety of normal in tank heaters over the years. Almost all of them tend to break sooner or later. I have used 3 inline heaters with my canister and it took the first one over 20 years before I replaced it. I have used Hydor ETH inlines and have both the 200w and 300w sizes.
https://hydor.com/products/eth?nosto_source=cmp&nosto=685264947
The problem with UV is for it to do what one wants the technical measures involved are important. Even the choose of bulbs matters.
What one needs to consider when choosing a UV unit would be:
- Bulb type and wattage. Most standard bulbs are too weak.
- Dwell time- this refers for how long water is exposed to the UV. This is determined by the length of the bulb and the flow rate of the water through the unit. The stronger the flow the shorter the dwell time.
- Turnover rate. This refers to how long it takes for all of the water volume to pass through the unit.
In addition, the specs needed to kill algae, to kill bacteria and to kill viruses varies. Obviously the more you want to kill the more important the above matters in choice of unit.
I needed basically to sterilize a Q tanks for the wild Altums. I did this in a 20 gal, using a 5w UV from American Aquarium. I plumbed it myself and it used a small variable speed pump to circulate the water. I spent a lot of hours reading on that site before I made my decision. I did a number of the calculations needed to insre what I got was the proper unit for the job it had to do.
Aquarium and Pond UV Sterilizers
TMC Vecton, Titan, Advantage-Highest Output Category A- Level 2 Capable
Only Full Service Authorized Seller of the TMC Vecton UV in USA
Check out the brands he sells and see why
https://www.americanaquariumproducts.com/uvc-sterilizers.html
edited for typos and grammar