Backyard Aquaponics
A place to discuss aquaponics

Ummm, no idea how I posted that 3 times, or that I had even hit the quote button.. Can a mod delete the self quotes above?

DanDMan: As I understand it, the bacteria in an FBF turn icky (and anaerobically produce hydrogen sulfide) if you cut off the water. Have you thought about transplanting the used sand into one of your growbeds? I don't know how your beds are setup, but I assume it would all wash into the bottom of the GB.

-ellie

I removed the sand from the system and spilled it. No big deal though I have my grow beds online now and my bead filter going in the breading tank.

Over the weekend I learned a few things about FBF's that are worth mentioning here.

FBF's work by suspending sand in turbulent water, balancing the downard pressure of gravity against the upward flow of water. (byap) If you are reading this, you probably knew that.

The minimum water velocity to fluidise sand. This specific velocity depends on the viscosity of the fluid. For water the velocity is influenced by the temperature and salinity of the water. (Wilkins)

From experimentation, I have determined the following.

Cylindrical shapes rely on the height of the filter and gravity to slow the sand particles. Any sudden burst of flow will wash the particles out of the filter. For example if you stand back to admire your work and step on the ingress hose, a small chance exists that the sand will wash out of the filter when you remove your foot. There is also s small chance that your SO will laugh at your expression when that happens.

Inverted cone "funnel" shapes are more common for FBFs because they allow the water and particles to slow as a function of increased volume, and are much less sensitive to pressure changes.

A couple of additional practical points..
A check valve to prevent sand siphoning back into the pump is a really good idea.
A Lowes fountain pump will seize when the sand siphons back into it.
Disassembling said fountain pump consists of unscrewing the prefilter, and impeller housing off the top of the pump, while the fish stare at you wondering if you are ever going to feed them.. .

and the #1 thing learned this weekend... RINSE YOUR SAND. Put the sand in a bucket and hose it until the water runs clear. "Play" sand nicked from the kids sandbox is surprisingly dirty. If all that had washed into the tanks I would have floaters this morning.

-ellie


References:
BYAP, Backyard Aquaponics forums
http://www.backyardaquaponics.com
Wilkins, Tony. Fluidised Bed Filters.
http://www.aquarticles.com/articles/man ... lters.html

Here is the link I couldn't find with the viscosity numbers...

http://www.calgaryaquariumsociety.com/A ... ilter.html

All good info! However, I thinks its worth using graded sand. It sells for under $10 per 80 pound sack at the local equipment rental place that sells 3 grades of sand blasting sand.

had some minor hiccups with the filter Ellie...we have all been there at some stage

hey! i missed all the talk about skmimmers

Fluidized Sand Bed Filter (FSB)

Good to see one in action Dan, thank you