There are a few principles I follow re equipment choices:
1. In the long run, the cheapest solution tends to cost the most up front.
2. I follow the KISS principle. "Keep It Simple. Stupid!"
3. If it ain't broke, don't fix it.
All three of those got me doing one thing over time. I use a lot of Aquaclears- close to 30 running at my peak and still have 19 today. My first hang-on was an Emperor 400. it went onto my first tank along with and Under gravel filter. Within a year I had to remove the UGF and I replaced it with an AC 200 (aka 50). The Emperor died affter about 8 yerars. I replaced it with the current model Emperor 400 at the time. It was on my tank about 10 minutes when I removed it, dried it out and sent it back. I only bought ACs since then. I will confess I did buy one Liberty filter (Eheims hang-on). I liked it but never added more as I like the idea of have all ACs and all Ehem Pro II canisters (3 running, one for 18 + years). This lets me keep a few replacement parts on the shelf without breaking the bank.
From day one I refused to consider any other brand of Canister. I bought a used 75 gal. set-up that came with a Fluval canister, I sold it and bough an Eheim. I laughed at SunSun. If you want to buy things that last a long time and are reliable, reputation matters. Eheims last forever it seems. ACs also last. The only AC I ever lost I had bought used and it has a small crack in the housing but did not leak. A number of years later when it did, I replaced it with another AC.
I should also say that all of my ACs have used the same basic media set-up. Two AC sponges (in some cases replaced using Poret foam) with a piece of batting between them. Some do not use the batting. I have a couple of ACs on my Altum tank and they each have a bag of alder cones between the sponges.
The only reaj changes that I have seen made to the AC hang-ons over the years is they are less sturdy. The plastic got thinner. The only places this has had an effect are the lids and the U part of the intake. The end that sits right above the impeller tend to chip. This, and lids, are about the only part I have had to replace. I remove the intake assembly to stop the filters and to clean the prefilter I add to them. All this off and on so,metimes results in the bottom of the U splitting or having a chip come of so the contact is no longer as sealed and the flow is not 100% any more.
ACs are, imo, the most versatile when it comes to media options. They are simple, which makes them reliable. Unlike many power filters you do not need to use any AC media if you do not want it. My best Eheim canister has 0 Eheim media in it. It has 100% Poret foam. Unlike my other two, which I clean twice a year, this one took 3.5 years before I had to do the first cleaning.
Most people who have the number of tanks I do have a fish room. My situation did not permit that. I would love to have a centralized fish room where all the filters were air powered and the media was all Poret foam. But my tanks are spread over two buildings and 4 rooms so almost every tank is independently filtered. I do have one space with six tanks where I have 13 centrally driven air powered filters and 3 AC filters. I have another pair of tanks (125 and 45L) in another room that run completely air driven.
One last observation about filtration. Only one tank I have ever had used a canister as it's sole filter. It was my high tech, pressurized co2 added, planted tank. I ran a single Eheim canister and I pushed the co2 directly into the filter intake. I did that for 10 years and it was my original Eheim which is still running great today. I always have at least one extra filter with canisters. This insures adequate O in the water. Biological filtration is oxygen dependent. If there is too little O dissolved in the water entering the filter, it cannot do its job properly. Moreover, that oygen is used and what exits the filter is depleted, to some degree, of O. The added hang-on helps prevent this from happening. I was not so worried about this in the planted tank as the plants made plenty of oxygen.
