Hang-On Filters - Why Your Aquarium Could Do Better
Lets first go back to understand the invention of the Hang-On filter... They were derived as a solution to convert aquariums to a wet/dry filtration system that in their own way were meant to remove the filter unit from within the aquarium to give you more viewing pleasure. Wet/Dry filters also, by virtue of gravity, have increased broken surface tension and therefore the potential to have increased water oxygen rates.
So .. makes sense, right? What could the problem be?
Lets compare the design with the reality...
Wet/Dry filters are filters that exist in the upper cabinet of the lid structure. The draw water from one side of the tank and return the filtered water to the opposite side, thus creating a slow moving circulation of the body of water.
Hang-On filters have their pickup within close proximity to the outlet. And herein lies the problem.
You will end up with the movement of water occurring around the filter. The Eddy current will circulate the water from the outlet back the inlet, thus you are cleaning the same body of water over and over and neglecting the rest of the aquarium. This is substantially worse in longer aquariums due to the insufficient circulation of water. Water not circulating is depleting in essential minerals, would be decreasing in oxygen, increasing in the amount of acid present, and encouraging algae growth.
Check out the image below to see what I mean ...
Unless they are used in very small aquariums, I would encourage the use of internal filters, canister (for medium to large aquariums), or the original wet/dry. In almost no cases do I recommend the of the Hang-On design, and if you do use one, it is almost essential to use one in conjunction with a powerhead. Want to know more - come in and have a chat with us.
The Pet Whisperer.