I'm interested in purchasing a Fluval 405 canister filter and am confused when they say it filters "up to" 40 gallons but the "pump output" is 180 gallons and the "filter circulation" is 110 gallons, what do they mean? What is the relationship of "output", "circulation", and "up to"?
I have a hex tank which has 50 gallons of fresh water & would like to keep the water as clean as possible.
I also have a 150 gallon tank outdoors for koi and was wondering about buying this canister filter for it.
Please advise..
Tom

The filter you are referring to is the 205 instead of the 405.
You will want the Fluval 305 for your 50 gal aquarium.

Up to : This is referring to the amount of gallons your aquarium is.
Example, you have a 50 gal aquarium, you will want to purchase a filter that is at least "up to" 50 gallons.
The fluval 205 is "up to" 40 gallons, which is too small for your aquarium,
So, you will want to purchase the next stage up which is fluval 305 which goes "up to" 70 gallons.

Pump out: This is referring to the amount of water that is taken in the filter and pumped back out into the tank in 1 hour. You will see the abbreviation GPH which stands for "gallons per hour".
If you see "pump out 180 GPH", this means that 180 gallons is being pumped into the filter and pumped back out of the filter into the tank in an hours time.


Filter circulation: This is the amount of water that is being completely filtered or "circulated" in 1 hour.
You may have 180 gallons going into the filter and getting pumped back out into the tank; however, some of the water being sucked back up through the filter may be water that was just pumped out.
The water further away from the water intake valve is going to take longer to get inside the filter, therefor only 110 GPH (gallons per hour) is 100% completely filtered through the filter in an hours time.

I hope this made sense to you. I know it can be confusing.
If you have any further questions, or don't understand my answer, please let me know and I'll do my best to further explain. :)

Is your outdoor koi set up an aquarium type tank or pond type tank?
This type filter would not do well if exposed to weather elements.
However, there are several filters suitable for outdoor use depending on what type set up it is.

Hi,
Thank you so much for this information. Answering your question regarding our koi tank, it is a 175 gallon horse water tank made of galvanized metal and we keep it outdoors. We use a fluorescent bulb kit to kill the algae together with a pump that flows the waterunder the bulb and a Penguin Bio-Wheel 330 filtering the water 24/7. We feel the filtering we use for the koi is adeguit.
Thanks again for your help,
Tom