View Full Version : fluidized sand bed

03-10-2003, 07:29 PM
what exactly is a fluidized sand bed? and how does it work?
could you set something like this up in a DIY wet/dry filter?

03-11-2003, 07:46 AM
I have not used one yet, but they sound good. the fluidized bed shoots the water up through the filter media, rather than pull the water through the filter medium. Because the water suspends the media, the fluidized bed doesn't clog up like other filters. its possible to build your own inexpensively. I will try one the next time I set up a tank. this page describes them well http://www.petswarehouse.com/fluidizedfilters.htm

03-11-2003, 08:52 PM
Thanks for the info!

03-11-2003, 09:40 PM
Check out this site for DIY. It's got fluidized filters.


03-11-2003, 10:52 PM
I would advise caution with fluidized beds. For a number of reasons.

Firstly, fludized beds (FB's), as noted above, are basically columns of sand kept in motion by an upward flow of water. As the sand material has an incredibly large surface area, the ability for a well maintained FB to handle large bio-loads is outstanding. Also, since the grains are constantly abrading each other there is no build up of organic mulm, and the system is, therefore, basically self cleaning.

Key Drawbacks:
1. The flow of water must be well calibrated to provide the necessary upward flow without flushing the sand out of the system. Impeller driven pumps will eventually deteriorate with age, and the flow will thus become impaired and bacteria die off will occur to some degree (see problem 3).
2. The biological functions taking place in the tower utilize a great deal of oxygen that would otherwise benefit the main tank's inhabitants.
3. The need for oxygen is so great, that in the event of even a minor power outage (i.e. just a few minutes) a full scale die off of the beneficial bacteria could take place (potentially leaving the system without biofiltration and requiring the system to be "cycled" once again over a period of weeks)...... That would otherwise be known as a Worst Case Scenario!

While very effective in very large operations (i.e. aquaculture applications with battery or generator backup), FB's shouldn't for the basis of filtration for home aquaria. The may serve a purpose as supplemental filtration though. I have used them on existing systems with the intent of moving them to new systems in an effort to "jump start" them. Still, they are just not as simple to use as other, more readily available systems.

Traditional Wet/Dry Trickle systems are more dependable and simpler to operate. If you are going the DIY route, I'd start there first. There are many ways to skin a cat, but Wet/Dry is very basic and very effective.

03-12-2003, 09:45 AM
Wow! Great info there chc, I had no idea FB's had such an achilles heel

03-12-2003, 10:59 AM
I had no idea of these drawbacks. either. It still sounds as though they may be good on a very large tank