Wow, it seems you guys are unanimous about not using a mechanical filter and going for a good protein skimmer.

I'm starting to learn that the nitrates are bad too and live rock filters that out. Now, here is where I am a bit confused and please point out if any of what I am saying is wrong: Live Rock as well as a cannister filter have bacteria that grows in them that converts ammonia into nitrite and then from nitrite to nitrate. So from what you are saying, is there a different bacteria that grows ONLY in the live rock that converts nitrate into nitrogen gas? These guys don't live in the cannister filter?

Second confusing point, whether you have a cannister filter or not, the amount of ammonia produced by the live stock will be the same which means the amount of available ammonia that gets converted into nitrite is the same. In turn, this means that cannister filter or not, the amount of nitrite available to convert into nitrate is the same. So how does the cannister filter INCREASE the nitrate levels? Wouldn't that be the same irregardless of cannister filter or not?

I don't mean to sound like I am arguing with you. I am not. It's just that I am confused and would like to find out why. It seems that all of you agree that cannister filters INCREASE nitrate levels so there must be some error in my thinking and that's why I am confused.

Here's one vote "for" the cannister filter. I've run one on my 45 for years with no problems. But as everyone here has said, you have to keep it clean. It's the build up of detrius in the foam filter that causes the problem. I clean mine monthly with a new filter (washed) and I also run a bit of carbon in a bag as well. I did run live rock in there but I stopped as the detrius buildup on it was just as bad as the foam and much harder to clean.
Go ahead and run a cannister, but like the rest of your system you have to take care of it.

Hi! So many ways to do it, I ran a filter for years no problem what so ever and am guilty
of not cleaning faithfully always. I used Ehiem Pro II can and used the media that came with
the filter. In having recently taken off all filters it is way easier IMO. The filter was such
a hassel and I will never go back. I did start with them though and don't know any different, hangover from freshwater days. It was a huge plunge to take them off and I watched everything like a hawk...expecting some slight change but nothing, wish I had done it years ago.
How big is your tank? Did I miss that. Just take it all slowly and follow the advice from here as it is great. And remember there is no one way so you have to really decide and
just go for it. When I first started I had the L.F.S only for info, did not know about Canreef and I managed. So good luck and keep us posted and ask questions galore!!!
It is addicting so beware, hehe!!! Opps almost forgot get and use a skimmer for sure if
you can't get both then only get the skimmer.
Leah

I'm running a sumpless 75 gallon at the moment, a 90 or 120 with a sump is in the future but for now the 75 is fine and running with a protein skimmer (old school air driven, counter current) as well as a Rena XP canister filter. I don't see anything wrong with your rationale with respect to the process of nitrification. Since you're very new to this, you don't come with any pre judgements regarding some of the equipment used and the processes involved in keeping SW tanks. I often see canisters given a bad rap and yes they can be a problem, but they can also work well. Live rock or canister will both do the job, but as mentioned, the canister is better run without filter media, except for carbon and perhaps GFO (granulated ferric oxide) for phosphate control. With sufficient live rock in your system, a canister is redundant as far as mechanical filtration, but in your case, as in mine, without a sump, a canister can add several gallons of volume to your system which is never a bad thing. It also adds a little extra flow but you'll definitely need some additional pumps/powerheads to keep things circulating.

When I first set up the tank (purchased used) the Rena canister came with it and the previous owner had ceramic media in it and not much else. Being a newb I read the instructions for the filter and proceeded to get all the 'proper' filter media to put in there, foam pads, more ceramic, plastic media, etc. etc. It really did get to be a pain to clean properly and after reading a little more on line, on forums such as this, I realized that it's best to run the thing empty, except for a bag of carbon. This is working well so far and after more than two years after setting up, my nitrates are undetectable. I must note, however, that from about the 7 month mark to 1.5 years after set up, I battled elevated nitrates. Also noteworthy is that there was virtually no change to these levels after I removed all the media from the canister. No matter what I tried, nitrates would return to between 20-40 ppm within days of a 30% water change. Therefore, in my particular case, I do not consider my canister to have been a 'nitrate factory', any more than my live rock. I really have no definitive answer as to why my nitrates are currently undetectable, my theory is, the tank has simply matured to the point where things are taking care of themselves in that regard. I also suspect the addition of first one and recently a second VorTech MP40W has contributed to cleaning up the nitrates. The greatly improved flow from these pumps is making life a lot easier.

So, based on my experience, by all means run a canister if you wish, but avoid filter pads, run it empty. For sure get a protein skimmer, even a crappy one will at least provide oxygenation, although you should be able to get a very good used one for a reasonable price, if new is too costly. Even if you are going FOWLR, don't skimp on the pumps for flow, it will aid the live rock in the filtration process.

Being fairly new myself, I remember the confusion.
Ok, here is an example of why i would use a skimmer instead of a canister.
Eg. Feeding time - some brine shrimp (or other food/fish waste/etc) is floating around the water column. The water current is supposed to keep stuff from falling on the sand/substrate. So, it can get sucked into a canister - if you have foam, it can sit there decompose until you clean it (image a fish sitter on holidays...). Or it can get sucked into the skimmer which would throw it into the foam in the cup. The foam isn't part of the system now (unless it overflows...) and it tossed out on a regular basis.

As for live rock, as I understand it (and someone may correct me on this), there is a special bacteria deep inside the rock which operates in anerobic conditions to help remove some of the nitrates. The rock also converts ammonia into nitrites and into nitrate, but it also has a small capacity to (remove/convert?) nitrates. Foam in the filter just lacks the ability to remove nitrate. (Also, how many times have you managed to rinse a sponge completely clean?)
A canister with carbon can provide extra flow, but a powerhead will provide more flow for less money (and lacks the capacity to leak water on the floor if it breaks). Just provides a nice place to hide some carbon.

Thought I might mention all my tanks are sumpless and relatively simple.

Just thought about something else to consider, while I was cleaning skimmers. It was a
pain where I live and that is when the power would go out I would have to unplug all
filters empty and clean them....that is if I was home was at home when it happened,
for me it was a huge job. Hope this is helping and not adding to your confussion.

since you are getting advice from persons far more knowledgable than myself all I will say is welcome and you have made the smartest move you can by joining this forum and asking questions

I think the thing to take away from the cannister vs no cannister discussion is that IF you clean them religiously, they're not necessarily an evil place to run carbon and GFO and if you had one already I would not dissuade you from using it.

However, since you don't already have one there are much more efficient ways to spend your money. Yes:
- You can run carbon adn GFO in it but you can also run carbon and GFO in a HOB filter that is easier to clean.
- You can put live rock in it, you can also put live rock in your tank.
- You can use it to increase flow, powerheads do this much more efficiently
- You can use it to "add a gallon or two" but really, on a 50 gallon tank I think the argument could be made that a gallon or two isn't really going to make a noticeable difference.

So really, since you don't already own one... I think the question you should be asking is not "Can I get away with using a cannister filter?" but, "Will spending money on a Cannister filter instead of other things benefit me somehow?" As an example I'll use J&L aquatics pricing (I know you found the 405 on ebay but I have no idea what the price was so we'll stick with J&L) A fluval 405 would run you $199. For that kind of money you could buy 2 Koralia 4's and a phosban reactor kit to run carbon & Rowaphos.

This can be a VERY expensive hobby if you let it. The key is figuring out which investments will get you the best returns, otherwise you could spend a fortune throwing good money after bad