Backyard Aquaponics
A place to discuss aquaponics

TC , the clacs are out there ,, but how much should we trust them?
An example is the "Kaldnes" bio ,, rated to dispose of 250 grammes of food per day per 50 litres of bio chips. Impressive but EXPENSIVE!!!! ( 250 grammes food is enough for say 15 kg of fish )
I've go round and round on this one ,, checked hundreds of sites , especially Koi sites because as we know Koi are dirty fish.
The best balance at reasonable cost seems to be "nylon pot scrubbers" in an up-welling style container with added air.

Just need to sort out some calcs that note the amount of needed air and the volume of media in some particular method coupled with the amount of fish it supports. And also need to know about the solids situation to go with it. I tried the solids removal by bottom tap on a swirl filter method and unless they come up with some way for it to happen automatically once or twice a day, I'm not into it. You leave it for more than 48-72 hours and the anaerobic stinking stuff that comes out the bottom is just way too nasty.

From what I read ,, an up-welling , pot scrubber- bioball filter with added oxygen only needs "back washing" once a week and a good clean once each 3 months. Should not be any anarobic problems if air is added and water has enough oxygen.
The calc's are all questionable , but pot-scrubbers do have a LOT more surface area than grow bed rocks.

Here's some calcs ,, how accurate I don't know ,, but he isn't trying to sell us anything so that gives it a bit more cred.
http://www.wernersponds.com/biofiltermedia.htm

the intake on my last filter sucks in a sh*t load of air, you can see it all bubbling through, sucked down the down pipe and up through the medium, I dont think it matters what you use as medium although pot scrubbers seem to be good, I have had great results using chopped up old garden hose, anything with surface area that is non-toxic will do!

I know I've heard of the pot scrubber type filters being used on ornamental and koi ponds and so long as they have a fair bit of air and are large enough for the pond/fish load, they can just go on without any cleaning out but I know that most ornamental stocking densities are so much lower than we go with that their numbers just don't relate.

I hate filters that require backflushing. I do have one but only because it was free and already hooked up before I discovered that I hate such things.

I'm waiting for Joel's details about the bio-filter/solids digester that is on the commercial system that he said would be in the next issue of the mag!!!!

So looking at the link. A pot scrubby filter should easily be able to handle say 3 kg of fish per 25 liters of scrubby filled filter provided there is enough air to support the bio-load.
(This is really just to put it into a context that most of use who are used to the rule of thumb -3kg of fish per 100 liters of flood and drain gravel bed- can get our minds around.) Or essentially there is about 4 times the surface area compared to gravel. Now this doesn't necessarily take into account how the scrubbys in a constantly flooded filter will deal with solids but that is probably largely related to how much air is being pumped in.

Now most of the other materials on the list either don't appear to have such a high surface area per square foot for their price to make them all that attactive. Like the bio-balls don't even have twice as much surface area as the 1/2" gravel so for the surface area it costs like over 5 times as much as gravel. The scrubbys on the other hand, cost a bit less than gravel for the surface area.

If space savings is all one cares about, then the activated carbon or poly beads or fluidized sand might do better for the space but with added complexity of the system operation and added upkeep and cost.

The only real added cost I really see for the scrubby or other bio-filter methods I can see is the possible need for extra air pumping to keep things sweet and fresh.

These are just some of my mental maunderings over the use of extra bio-filters instead of just using gravel beds.
Thanks for posting those plans, helpful for people who need to keep fish alive but for whatever reason can't have the standard gravel bed hooked up for some period of time.

These bio-filter plans could be really helpful for those people who due to space/weight situations are doing NFT pipes instead of flood and drain gravel beds.

The other possible benefit is for those that want to grow warm water fish in cooler climates,..... even a hot-house green house tends to be cool come 4am in the morning ,, so switching water flow away from the beds and into the bio-filter from 4am - 8am would see a huge temperature benefit.

bentaz,

Thanks so much for this great post! I've been puzzling a small commercial raft system and the last piece of the puzzle is sorting out the filtration unit(s). Like TC, I'm looking forward to the next issue of BYAP magazine for the very reason she states... details on the solids digester.

I live in an economically depressed region of the US and am hoping to create a simple low-cost system that is easily duplicateable for people with small plots of lad to build and generate income. May take a few years to really get where I see this going, but posts like this really help with a plan to make this area more self-sufficient.

Thanks,

CB

Hi I like the wheelie bin one i have been looking for something like that to over summer trout [no need to use growbeds ] does anybody see problems of making a few adjustments
still use the milk crate [only with 1/2 the depth ] useing the vertical pipe like chift pist taking the water from the bottom running the water down through the filter medium with a dacron on top [washable caching the large stuff]
also i have a spar blower running that right to the bottom to back wash the filter media also is it worth while to put an air stone in the bottom to add air
Ah the possabilities are every where

My 150 gallon Aquarium has about a 40 gallon aquarium for the biofiltration. And it does have prefilter media to remove solids which needs to be replaced or cleaned. Also the plastic bioballs are quite large and do not seem to have near the surface area scoria has. I like Bentaz's wheelie bin setup.

It is simply innacurate to compare grow beds to a filter ..... beds usually flood and drain 15 on 45 off ..... a filter is normally 24/7 and has the advantage of bio-filter media in moovement ,, I would suggest a reasonable and cheap bio-filter would out perform a grow bed 10 times it's size ..... more likely 50 times.

IF the solids are pre-filtered out and the bio-filter has enough aeration, then no doubt for the space, the bio-filter is going to convert more ammonia and nitrite than a grow bed. However, this adds several things to a system.
1- the solids filter and the cleaning/maintenance of such.
2- Need more aeration to keep the bio-filter functioning properly.
3- now need another place to grow plants to use up the nutrients or have to do regular water changes.

An external bio-filter does not necessarily save anything on a regular AP system, it just re-arranges it. As in it is just another way of doing things. Perhaps a little more complex than simple gravel beds but for those who only wish to grow lettuce and perhaps some herbs in tubes and can't have the grave beds due to weight and growing indoors, well definitely build some bio-filters.

Thanks for the pics Bentaz
What is your flow rate through that pvc pipe filter (ie fast, medium, or slow)?

Alternative view,,,
Bio filter stops beds filling with so9lids that cause anerobic pockets killing fish ( numerous examples here in BYAP)
Bio filter requires back-wash perhaps once a week , time less than 20 seconds ,, growbeds as stand alone filters clogged with solids take numerous hours to remove gravel and wash wash wash , and quickly once again have anarobic problems.
The movement of the filter material within a well designed fillter is the key and significant advantage obver a bunch of rocks sitting still.
No need to add more plants ,, what is this dream?? from what i see most AP ers LACK nitrates ,, look at OBO ,, he is adding pure Ammonia to try and get more Nitrates.

Any additional aeration is a significant gain in a system.

Put simply ,, a well designed bio-fliter , saves space , helps reduce the chance of anaerobic problems , allows greater conroll over temperature swings and allows for a more managed system.