filter gph vs. effectiveness

you have 2 remember that there are 2 types of filtration...bio and mechanical. IMO....eheim filters don't really focus on high gph, they focus on their storage of bio-media. If you are looking 4 high gph....go with a fuval fx5 (2 me it works more on the mechanical part)...more water movement but not to much bio-media. But 2 me...if u want the best of both worlds....build or buy a sump/wet dry filter that can hold a good amount of bio-media and invest in a good pump that can put out as much gph as u want 2 have. But if you don't wanna go that route u can read this....hope it helps ya?

http://www.monsterfishkeepers.com/forums/showthread.php?t=68458

It's the media holding volume that counts for filtration, not the flow rate although a sufficient flow rate is important. You also want a good flow rate for water movement or low flow rate if keeping delicate species/swimmers. Get an eheim with a relatively low flow rate and you can supplement it with the desired powerhead for water movement if needed.

I like filters that can get the job done with less flow. They're cheaper to operate. Most of my wet/dry filters are turning the tank over 3x per hour.


If you would measure the actual output vs the advertised output on your current filters, I think you'll be surprised
You may not be flowing as much water as you think.

rallysman;1919102; said:

I like filters that can get the job done with less flow. They're cheaper to operate. Most of my wet/dry filters are turning the tank over 3x per hour.


If you would measure the actual output vs the advertised output on your current filters, I think you'll be surprised
You may not be flowing as much water as you think.

Click to expand...

I know this to be true. I have Fluval 403 (yes I know its old) but it calms 317 GPH. well using a 3 gallon bucket and stop watch I find this to be less than accurate. In their defense it never states at what head hight it can put out that rating.

nfored;1926369; said:

I know this to be true. I have Fluval 403 (yes I know its old) but it calms 317 GPH. well using a 3 gallon bucket and stop watch I find this to be less than accurate. In their defense it never states at what head hight it can put out that rating.

Click to expand...

and they measure them without media.

When you look into buying a filter you look at gph. However you also have to look at the amount of media as well. EHEIM is a good filter that does come with a lot of filter media. It is always a good idea to overfilter though and go with fluval thats my favorite and I trust those on my reef tanks.

Flow rate is irrelevant. Single pass efficiency is more likely to be achieved at lower flow rates. If single pass efficiency is not achieved, then any consumables that pass through will get their chance the next time through.

With that said, if you want to increase the consumption rate, you have to increase the bacteria population which means increasing the bio-media.

One other note, marketing firms are tasked with getting consumers to buy their clients products. They are not tasked with understanding the science behind them. Pretty much when you buy a pump or filter, it is like you are buying it from a used car salesman. If you try to educate yourself from what is highlighed on the box or other advertising, you are really at the mercy of the marketing firm.

For instance, a cheap pump can compete with a quality pump simply by advertising the flow rating (which is measured at zero feet of head). At working height, the cheap pumps rarely measure up. (see the pump sizing thread in the sticky section for more info.)

Another example of marketing garbage that we have to deal with is that Quiet One pumps are advertised as being energy efficient. Equivalent pumps by Danner Supreme use almost half the electricity.

As stated above… we have to separate mechanical and bio-filtration in both our minds and our words…

Nothing is more important than gph… for mechanical filtration… yet for bio filtration gph is a minimal impact…

I personally feel that “bio-filtration” is one of the best industry hypes that the aquarium trade has produced. I have several tanks that are running off of an AC HOB with one sponge and no rings… no other ‘bio-media’ what so ever… and they have zero ammonia and zero nitrites 100% of the time…

It is completely true and valid that with nicely modified bio-filtration, the bacteria colony can increase much (much, much) faster to accommodate an increase of bio-load (I.e. adding fish)… But without such bio-filtration bacteria will still form throughout the tank/filters and do everything that they will do in fancy bio-media set ups.

Based on the above understanding, I feel that bio-media is a nice safety net to have in place, but is far from “necessary”.


I personally like for my filtration to handle the bulk of the waste that accumulates in the tank. Therefore I use high flow rates to push the waste to the filter’s intake.

One can very validly argue that this is also unnecessary as the owner can easily remove the waste during regularly scheduled maintenance. I could not argue that point at all…


In the end… enough water movement to prevent stagnation and to promote oxygenation is necessary… beyond that there are a lot of paths to take in improving filtration to account for other things… such as nurturing a bacteria colony or removing waste…


This is the philosophy I’ve come up with after screwing things up for man years… and finally finding a method that works for me…

I wish you the best of luck finding an approach/philosophy that works for you…