Fluval 103 Multi Filter
390 Liters per Hour (103 gph)
Fluval 203 Multi Filter
420 Liters per Hour (111 gph)
Fluval 303 Multi Filter
840 Liters per Hour (222 gph)
Fluval 403 Multi Filter
1200 Liters per Hour (317 gph)
Hagen - Fluval Series 3 Canister Filters
I have been using a Fluval 403 for several years in an unusual application. I have an indoor flight with about 40 finches, budgies, softbills and cockatiels. I set up a bird bath with the Fluval circulating and cleaning the water. I just disassembled and cleaned it, and I agree with the complaints about how difficult it is. I suspect all canister filters have this problem. It is hard to position the O-ring properly. You have to test the assembled filter with air pressure before filling it with water, or else you have a big mess. The filter is very powerful and certainly does its job in a demanding application. It keeps working even when bird seed sprouts inside. I am able to change the water every few days, so it stays fresh even when 40 birds bathe and crap in it.
I have 2 Fluval 403 filters on a 125 and 90 gal tank. They do a wonderful job, but I usually break off the plastic tabs on the impeller cover. This time I got lucky, but to my surprise I think the magnetic motor is fried. I always swore by these filters as they are quite easy to change and clean ( I have 2 Magnum 350's on the tanks too and the impellers eat through the plastic sump and make a wonderful flood every once and a while). I also have an Eheim 2229 and 2227 which are wonderful but truly a horror to clean with all the o-rings. I just can't believe that the motor burned out, but would recommend the Fluvals over the others for ease of cleaning and price.
I have used the same Fluval 303 on my 75 gallon tank since 1989. Only parts I have replaced have been O-rings. I clean it every six months and the major difficulty is connecting the input and output hoses with no leaks. Yes, you also have to be careful with the main canister O-ring when reassembling the filter. I keep mine running inside a two gallon bucket beneath the aquarium. This makes it easier to check for leaks and move. I have used this with undergravel filters and now with a biowheel and it has done the job for me for a long time. The impeller assembly has outlasted many powerheads.
I have had a Fluval 304 for about two years and as a first canister filter it was OK. As others have said it is a pain to clean and is fragile. The impeller broke and then I bought a replacement impeller and it still was broken. I also cleaned it every 2 weeks. So instead of buying a new fluval I bought a Eheim Pro 2. The Eheim is a lot better except that the intake and output are swiched right to left instead of left to right like on other canisters. I give fluval a 5 out of 10 and think if you want good filtration buy a Eheim which I give a 10 out of 10 for the Pro 2. Other Eheims get a 8.5 because they do not self-prime.
I have been using a Fluval 403 on a 90 gallon freshwater tank for over 7 years with no problems. The o-ring is only tricky the first or second time...after that it is very easy. The only parts I have broken have been one of the tank clips and an ear off the impeller cover...not bad for 7 years+. Any serious aquarium hobbyist should keep a supply of spare parts on hand for any filter or pump...just common sense. Keep an extra o-ring, set of clips, impeller cover and o-ring, and an impeller and your Fluval will last many many years. I would rate the Fluval 403 a 9 of 10.
The fluval 303 is a great tool for the aquarist, I don't understand why people don't like the o-ring. If you read the directions and use some common sense when installing the ring, they never fail. I've not lost one drop of water due to o-ring problems. If you do, maybe you didn't read the directions carefully enough.