main difference between HOB and cannister filter?

You can fit a lot more media in a canister.

a lot more media... they are a bit more effective as well

the reason for this is mostly due to the increase in media-- and usually they have a higher flow rate compared to comparable HOB filters

HOB's use the pump to pull water up the pick up tube.
many cannisters use siphon to bring the water to the cannister and the pump pushes the water up to the tank.

I personally think cannisters need more surface/media . for the bio media and mechanical filtration to work properly .
they do tend to move more water so subsequently they need more surface for the filter to remain effective.

Canister filters are
Str8 mechanical filtration they do not let water bypass filter media.letting you custom stack with things like white dimond chips Ect and finer and finer filter pads to remove the bad stuff.but they do little in the way of Bio filtration
As they are air/water tight.with HOB filter you give up a lot of
Mechanical filtration
You gain Bio filtration do to them being open to the air

IMHO for FW tanks of
150gl and less HOB's will work fine.FW tanks over 150gl and any size SW I would use nothing less then a canster

On a 60 gallon tank with average stocking, I would run a canister from the bottom and a HOB up top... both rated for something in the 75-100 gallon range. Start off with whichever filter you have, then watch for sales, discounts, or used equipment for sale over the following months to get the second filter.

I like canister filters best because they move more water and I can pack the media trays with whatever I want. But I also want a secondary HOB running for more biological filtration. I can stuff it with carbon temporarily to pull out meds without having to open up the canister for this. What I don't like about HOBs is they hold very little media and as soon as that starts clogging up, the water flows right over the top, doing no good whatsoever.

McLendon said:

Canister filters are
Str8 mechanical filtration they do not let water bypass filter media.letting you custom stack with things like white dimond chips Ect and finer and finer filter pads to remove the bad stuff.but they do little in the way of Bio filtration
As they are air/water tight.with HOB filter you give up a lot of
Mechanical filtration
You gain Bio filtration do to them being open to the air

IMHO for FW tanks of
150gl and less HOB's will work fine.FW tanks over 150gl and any size SW I would use nothing less then a canster

Click to expand...

Not all completely true. Canister filters are NOT just for mechanical mechanical filtration, they do have bypass(not much though) and have great biofiltration(more room for media than a HOB).

HOB filters dont gain any benefits from being open to the air. Matter of fact all the media should be submerged in water in the HOB.

Main reason I have always used canisters, is that they dont make a lot of noise, and keep surface agitation to a minimum.

Canisters are available for all size tanks down to nanos. Really just depends on the application and personal preference.

McLendon said:

Canister filters are
Str8 mechanical filtration they do not let water bypass filter media.letting you custom stack with things like white dimond chips Ect and finer and finer filter pads to remove the bad stuff.but they do little in the way of Bio filtration
As they are air/water tight.with HOB filter you give up a lot of
Mechanical filtration
You gain Bio filtration do to them being open to the air

IMHO for FW tanks of
150gl and less HOB's will work fine.FW tanks over 150gl and any size SW I would use nothing less then a canster

Click to expand...

This statement doesn't ring true with my experience. The only time that I use a HOB filter is if the tank is so small that you don't have a choice. Canister filters are biological power houses! The largest canister that I ues is the Fluval FX5 and all I use is ceramic bio media in it. Every try is filled with it. The only mechanical filtration that I use with the FX5 are the sponges that surround the bio media within it. I have no issues with particulates in the water or anything like that.

I read that a lot of people put a lot of emphasis on mechanical filtration. Yes, it's OK to have, but the bio filtration is far more important. All canister filters come standard with mechanical filtration. You shouldn't need to add floss, pads, etc. You're just going to clog up the filter faster. Put bio media in every tray. You don't even need carbon if you are keeping a reasonable maintenance program.

Keep your tank as natural as you can! Use bio media to the max and stay away from chemicals and all the other crap that costs money! Once you set up a canister filter, you shouldn't have to keep spending money on it. Just clean the sponges once a month! Bottom line, canisters offer more bio media surface area. That is all.

Best wishes!

I will add the following:

Canisters allow you unlimited flexibility in where you place your inlet and outlet. With HOB you're stuck with one configuration.

If you're running a planted tank, and/or you want less surface agitation for reduced evaporation, canisters allow you to reduce this factor.

Canisters (especially Eheim Classics) need far less maintenance and don't require costly proprietary media. In fact my Eheim Classics have never had any media replacement. I just rinse it every few months.

Physically I like the notion of less weight and less stress on the tank. Also requires less cut away on the back strip of your lid. Decreases evaporation and helps reduce risk of losing jumpy fish.


HOB's are generally less expensive to purchase, far easier to use and maintain.

HOB's are often better for systems where you want increased gas exchange - a lot of marine keepers like them over canisters due to the claim that they aren't as prone to produce nitrate.

echoofformless said:

HOB's are often better for systems where you want increased gas exchange - a lot of marine keepers like them over canisters due to the claim that they aren't as prone to produce nitrate.

Click to expand...

I'd love to hear the explaination behind less nitrate in an HOB.