I understand how an aquarium foam filter works in principal as far as biological and mechanical filtering is concerned. My issues involve volumes – such as the volume of water flowing, the volume of air needed to move the water, and the volume of bacteria on the filter material.
My question is how are these foam filters rated?
Is it volume of foam?
Is it the tube size where the air and water flows?
Why is a 3.5 inch cubed filter rated for 10 gallons, but a 7 inch cubed is rated for 30 gallons?
It is twice the volume – not 3 times so that makes no sense to me.
The air “lift” tube is the same on both.
Is there a spreadsheet or formula one can use to compute the water movement through such a tube?
How would you measure the weak air pressure from an aquarium pump?
This leads into other questions about these filters such as…
Why not a 100 inches cubed with a 120 gallon per hour power head for a 30 gallon aquarium?
Other than the displacement in the tank, would it not be a better match for the load?
If the flow rate is so low, why is that acceptable when we would want higher flow rates in a canister or hob filter? The suggested rates for those filters are at least 4 times the tank volume per hour. Hence a 30 gallon aquarium needs a 120 gph flow rate.
Is there any studies that say 7 inches cubed is the perfect size for up to a 30 gallon tank?
If so where can I find them?
How do I know that enough water flows through the sponge?
Please no novice answers.I feel pretty well assured I understand nitrogen fixing bacteria in principal.
I do not know the area of bacteria compared to the bio-load of a fish tank.
Do not be afraid to send me engineering formulas. Those are most likely the answers that will serve me best.
Per inch which gives the greatest filter area – a sponge filter or a ceramic filter of the some volume?
I recognize the greatest filter volume for a given area many well be the fluid sand filter, but it has an appearance issue.