Best filter for 100 Gal

For a planted tank, where you want to minimize surface agitation, I think a Fluval 404 would be best.

An Enheim would be good if you can take out a second mortgage.

As was touched on above, there is a lot more info needed to answer this question, i.e. Planted or not, do you want silence, or does trickling water relax you, wha tkind/how many fish do you have in mind etc. I just set up a 115 and have an RFUG/ an Emporer 400, and an AC 500 in place on it. But it will be home to some big messy fish, and very few plants. The water noise isn't an issue for this tank and so on. There are many options depending on your plans.

I use an Emperor 400 and a Tidepool2 filter with CSL 2x helix UV sterilizer in a non-overstocked 180 and it is has excellent water quality and clarity. I got mine for $140 with their catalog code (gets you specials). It is easy to use and provides me room for return pump and UV setup. Just an idea but I like it a lot.

I have an Eheim 2028Pro in my 120g, planted. Very quiet and seems to be build solid and I heard nothing but good things about Eheims. As with many filters, you can adjust the flow so it will work with many applications.

Falcon

For sure get a canister filter. I use a fluval 404 and I'm pleased with it. I think that the HOB type of filters cause more surface agitation thus reducing the amount of CO2 in the tank which is a bad thing for planted tanks. Over the long run a canister filter saves money and time too.

I would suggest at least a couple of canisters for your tank. Why two? Redunancy. Its always better to have two smaller filters, rather than one large one (ie. 2 AC 150s, compared to one AC300). Having multiple filters will give you a form of insurance. If one filter breaks down, the second filter can pick up the slack of the broken filter, giving you time to go grab another filter. You can also alternate cleaning the two filters (ie. clean filter one this week, filter two next week, etc.).

You're canisters should have some kind of prefilter on its intake, to prevent debri from entering the filter. This is a good thing because it reduces on the maintanence of your filters. There was a period of time when my Fluval 404 was not prefiltered (on my Malawi tank), and I was constantly cleaning out the filter. Now that its pre-filtered, all I do is rinse out the pre-filter once a week. The last time I cracked open my filter, it was still clean.

If your plant tank is heavily planted, then you need mostly mechanical filtration since your plants will do a large majority of the biological filtration. Fill your canisters with mechanical filtration media.

Currently, my 70 gallon plant tank has two canisters running on it, an Eheim 2026 Professional II, and an Eheim Ecco 2234. Both canisters have never given me a problem. I also have a Fluval 404 thats been running for 2 years now, and that has also never given me a problem.

HTH
-Richer

i would suggest getting a sump, but that's just me.

I enjoy "live" planted tanks and would suggest a Rena Filstar xP-3 canister filter(s).....