Backyard Aquaponics
A place to discuss aquaponics

Ok I have been searching most of the afternoon, and I am wondering what kind of media everyone uses in there bio filters? I am looking at K1 media but holy cow its pricey. I am looking into finding LDPE beads but not really having luck finding any. But what about bio balls etc? ok and GO

Dufflight used 13 mm irrigation poly pipe cut into ~1cm lengths to replace k1.

There is a competitor to k1 that is much cheaper....WaterTech mb3.

Sleepe used bottle caps.
I just use scrunched up shadecloth.

If you want to combine a filter and a self cleaning biofilter into one unit I would go HDPE beads, good surface area,sg and the ability to rotate. If you want to source them go to a small plastic extrusion/manufacturing factory and talk nicely to them.

My last filter uses bioballs (personally I think they are a pain in the ass) it was the one before used bottlecaps (the one that Rupert keeps making fun of ).
There is one bioball I would possibly like, small about 1/2 to 3/4" with no spiky edges, I have a few but have not seen them again. There is also spiral wall plugs which would be great chopped up but I think they have been discontinued.

If there is anyone good at maths I would like to know the surface area of a standard soft drink bottlecap.

Just as well they didn't put a deposit scheme on bottle caps...

I worked this out years ago (K1 is really cheap)

Trout does that include the inner surface?
It cant include the thread on the inside, or the grip on the outside.
I wish i knew maths, it has to be a bit higher than that though i think.

Trout, I suspect that the standard(?) bottle top of today must be smaller than they were when you made your measurements and calculations years ago. For instance, none of the tops that I measured were greater than 30mm diameter, and they range in height from 10 to 16mm!

Offsetting this reduction in size, from the point of view of usable surface area for bacteria colonisation, is the fact that both the inside and the outside of the sides of the bottle top are crenelated (for thread on inside and for grip on outside), which I believe would at least double the area of these surfaces.

Edit: It seems you beat me to it, Yavimaya!

Although the cost of Kaldnes is up there.... its the surface area and proven track record you paying for.

I would fork out for the K1 as its the best around

Yes, the outside surface area is 0.0028 m2 which I just doubled to include the inside as well.

Bearing in mind the plastic thickness is 1.8mm hence internal area would be less than the outide.







By doubling the outside area rather recalculating the smaller inside area,

I used this method to compensate for the thread and knurling.

I measured the top with a vernier, otherwise to do it as you suggest I would have to

take it in on the profile projector and that becomes a three hour job.

I don't think that would be a worthwhile job as every company makes a slightly different top.







I think the thread is standard but the cap design will vary according to the company requirements

and their product advertising campaign.

And if you begin to include child proof caps in the mix the maths will be very varied and as you've

mentioned the caps you have range in height from 10 to 16mm.

So I measured the cap I have and showed how I worked it out so that if you have caps that are

different you can follow the workings and work it out for your size tops.


cheers Lou

City i used a MB3 for my bio filter much less expensive than K1

Warter Management Systems

Thank you Trout, that gives me something to work with.

I will fill a 1l container with caps and see how many I can get in I have approx 720l in the GB.

I would go with HDPE pellets if I had a choice for a biofilter/filter. They are cheap robust and have the advantages I mentioned earlier: unless K1 drops in price they are a rip off. Its all very well having a very large surface area but in practical terms using a very small biofilter means more cleaning and although they say it wont I suspect a large influx of for example dead algae would give it a hard time ( this is not based on me ever having any though)

Yeah k1 is the states is not cheap at all, I will have to call the makers of mb3 because there is no price online. I found a 12lb of LDPE for like $25 which is not bad I called a lot of plastic shops here and none of them make and or use them. And I am way to lazy to collect that many bottle caps.

There's nothing wrong with using "bio-balls" in small filters...

The K1 Kaldnes was designed for larger scale filters and heavy feed rates... and in those applications... not only works exceptionally well.. but in comparison to other filter/media combinations...and ease of application.... is fairly priced...