Though expensive, I bought the Fluval G6. Just love the ease of cleaning the mechanical filter. I don't have to disconnect anything. Just close the valves, flip up the little cover on top, pull out the mechanical and/or the chemical cartridges. Done in 5 minutes, So easy! Now a comparable DIY at half the price would be an amazing project.
From what I read people were comparing GPH and weren't too impressed with the G6's rating. But I know that GPH isn't what's important to ME. It's the large biological filter capacity and EASE of maintenance. But I don't know why owners gave it 3.3/5. I've only had it for 1 month, so I really can't give a proper review YET. But I have done a couple of filter cleanings so I know how easy it is to clean the cartridges. 30 years ago I had a vortex canister and hated to clean that, so the G6's design won me over instantly. It's just so darn expensive. The G6 is pretty big and holds lots of biological media and I know that is what's really important. I cover the inlet with a pre-filter to prevent crap from going into the G6. My mechanical filter wasn't that dirty at 2 weeks, so I'll probably do a monthly cleaning. I run with charcoal 24/7 and plan on changing that once a month, so a monthly schedule seems like a nice low maintenance routine! And with AquaBella, I'm hoping for monthy 25% water changes also. So far (1 month since starting the tank), my tank has been rock steady with all parameters.
The G6 has some electronic monitoring also, which isn't that important to me. But I have been using the EC readings. I know my tap water is hard and it was reading about 400, so I've been using the readings to help me lower the hardness as I did water changes with distilled water. It's at 295 now and I just recently bought the API GH & KH test kit which shows KH of 4 and GH of 125 which is still a bit hard for my cichlids. So I'm planning to monitor the hardness and ion concentration with the EC reading. It's a quick way to see if I need to test the water conditions. It's interesting to see a higher EC reading in the morning after the lights have been off for 12 hours and then see it gradually go down after the lights are on. Not sure why; there is a 10 point swing for my tank.
As for the G6 filter, I bought it for the large biological filter capacity/ease of maintenance. I also have fluval C4 mainly for mechanical filter and it's ease of maintenance, and the AquaTop for it's UV light. I hate cloudy tanks, so these three filters for my 34G tank are doing a terrific job so far.
The bacteria live in a biofilm which adheres to solid surfaces. There is a flow rate in any system that will blast of them off the surface but i am not sure there is a formula for it. one reason is that not all biofilms are equal. One reason behind the design of bio-wheels is that the rotation cause the bacteria so spear out more evenly over the surface rather than building up thickness. the thinner the biofilm, the more aquadynamic (to coin a phrase). So how does one create a formula to account for difference in biofilm formation?
The there is the whole flow rate vs contact time consideration. For the bacteria a slow rate is better because it keeps them in contact with things longer and give them a better chance to extract them. That conflicts with a higher turnover rate for removal all wastes. One solution is to a large internal volume in filtration which is some of the reason sumps are so good. A faster rate of flow in and out but less current over the media between them. You have more media space in a decent canister than a hang on and a sump is even more.
Can you not go to a site like Eheim's and look at their specs and use them as a guideline. They should show volumes, diameters and flow rates. You could even do this at other manufacturer's sites. Then decide if their method is satisfactory for you.
In any case, good luck with it- I am in the buy it camp so i can only help with the bacteria part. I can confirm that about 80f is a good temp- the bacteria will be killed at sustained temps somewhere between 104 and 110. Over that and they will be killed fast. They can also not tolerate being frozen but I really doubt that is an issue
I recently received one from a customer whose Discus outgrew its capacity. He has a 150 with a dozen large Discus, and at least 50 other fish, mostly assorted smaller Tetras. The G6 worked well for him for about two years, but as the Discus started getting into the 6"-7" range he decided he needed a more powerful filter so he bought the big Eheim with all the whistles and bells. I'll be taking care of his tank for the next month while he's on vacation, so I'll get a chance to check that one out as well. Two years ago when I watched his tank I was very impressed with the ease of maintenance on the G6, so when he asked me if I wanted it I jumped on it. I have no doubt it will more than adequately handle my 75 gal after I evict all of the assorted tropicals and convert over to a native tank for my Pickerel, Perch, and a couple of Sunfish. And the ease of maintenance is second to none among canisters. As far as all the whistles and bells, a few years ago when a Fluval rep came to the place I was working to demo one, I immediately thought that if they could install a conductivity/salinity meter in it, they might as well have installed a controller so it could run an ato unit. That obviously never happened, but it is really easy to maintain, and I didn't have to pay $400 for it.
