biofilter start-up, biomedia doesn't sink

[bencda]

Hi everyone,

I'm starting up a seawater moving bed biofilter and purchased some new plastic bio-elements. Although the density of the media is ideal, they do not integrate into the water column and stay on the surface, even with harsh aeration.
I would like to ask if you have any suggestion on how to quickly sink and make the media move?

Thank you in advance.

 

[Rocksor]

Picture of the plastic bio-elements? What brand?

 

[bencda]

Picture of the plastic bio-elements? What brand?

Brand: RK bioelements
its made of polypropylene

 

[wednesday13]

If its comparable to k1 media, it will take a good month or longer to build bacteria and “boil” properly. No fresh media “works” from the rip in a moving bed/reactor.

 

[fishdance]

Super strong strength bath of Potassium Permanganate to strip off the shiny new coat will abrade/pit the surface microscopically. This will sink the media much faster and hasten biofilm colonisation.

Any oxidiser will suffice but PP rapidly decomposes by itself.

When I don't have any fish in the tank/pond, I add cloudy ammonia solution and some aged media so beneficial bacteria are already coping with high level loads before fish are added.

You may have to add the media in batches a week apart if your filtration volume can't handle all the new media at once.

 

[bencda]

Super strong strength bath of Potassium Permanganate to strip off the shiny new coat will abrade/pit the surface microscopically. This will sink the media much faster and hasten biofilm colonisation.

Any oxidiser will suffice but PP rapidly decomposes by itself.

When I don't have any fish in the tank/pond, I add cloudy ammonia solution and some aged media so beneficial bacteria are already coping with high level loads before fish are added.

You may have to add the media in batches a week apart if your filtration volume can't handle all the new media at once.

Thank you for the answer.
Interesting, so its more about removing the media coating instead of decreasing the surface tension of the water?

 

[esoxlucius]

A little background info for you.

Freshwater has a specific gravity (density) of 1.000. Any plastic with a SG of less than 1.000 will float in water, any plastic with a SG of greater than 1.000 will sink. Polypropylene has a SG of around 0.905, which means it is extremely buoyant in freshwater. Bearing in mind you are using your media in saltwater, which is slightly greater in SG than freshwater, then you can understand why your media isn't sinking. It will be even more buoyant than usual, as you are discovering.

Manufacturers of these plastic medias which are meant for moving bed filters can, and should, though I don't know if they do, add harmless "fillers" to the polymer mix before processing. Only a slight % of filler will make the media less buoyant and that way you will have a media that works as it should. It would seem that your media is just pure unfilled Polypropylene.

Hopefully fishdances little tip works for you, if not at least you will understand why.

In time, as the BB colonise the surface of the media, this might make it less buoyant, who knows.

 

[twentyleagues]

I agree with F fishdance and esoxlucius it will eventually "boil" properly. It will take a few days to weeks to build up enough biofilm to make this happen. You should look into biopellets for salt water much more effective.