To filter or not to filter, that is the question...

[Cris Meeks]

I'm currently in the process of building a larger system but am very new to AP.  If the plan is to add worms to grow beds I'm thinking that any particulate filtering needs to be "post" grow bed not pre or will I even need to filter if I am hoping to run flood & drain beds with a bell siphon?

[Don Cole]

Good question. I have a 900 gal. system with two 4x8 media growbeds. I dont have a filter pre or post growbed. My understanding is that the media beds ARE the filter that provides for the breakdown and mineralization of the solids. Now, I am looking to build a NFT system and use the same fish tanks and was wondering the same thing, should I use the return water from the growbeds for the NFT or set up a solids filter from the fish tanks to supply water to the NFT? I dont mean to hijack your post but I think our questions are simular.

[Cris Meeks]

Don, As a long time aquarist I think that you will always have to provide a mechanical filter of some kind to stop the build up of a compost pile in your biological filter.  Your grow beds are basically the same as gigantic bioball tray as they provide the substrate to support the populations of bacteria to pull ammonia (read fish pee) & nitrites (read bacteria population #1 pee) out of the water & turn them into the nitrates that the plants are using.  Fish poop is a different story.  It has to be converted somehow (read composted) for the plants to be able to use it.  My question is are the worms going to accomplish this composting in such a manner that they will not affect the water quality to the detriment of the fish? With aquariums you have to remove the solid waste from the system every so often to keep it healthy.  Can I bypass this by growing worms that need the fish poop to feed on?

PS    NFT?

Don Cole said:

My understanding is that the media beds ARE the filter that provides for the breakdown and mineralization of the solids. Now, I am looking to build a NFT system and use the same fish tanks and was wondering the same thing, should I use the return water from the growbeds for the NFT or set up a solids filter from the fish tanks to supply water to the NFT? I dont mean to hijack your post but I think our questions are simular.

[Don Cole]

Cris,

My understanding from everything I have read is that the worms do metabolize the solid waste and produce castings that are primarily minerals and nitrate. There are way more people on this forum that are way more knowledgeable on this than I am. I was just hoping to kind of ride your coat tails on this subject for my own answers.

NFT (Nutrient Flowing Through) it's a hydroponics technique that has been adapted for aquaponics. Flowing water through tubes with plants suspended above the water level that draw nutrients from the water. 

[Cris Meeks]

Don, guess I should have asked prior to crawling up on my soapbox, do you currently have worms in your growbeds & if so, how long have they been in operation?  What kind of fish are you raising?

Don Cole said:

Cris,

My understanding from everything I have read is that the worms do metabolize the solid waste and produce castings that are primarily minerals and nitrate. There are way more people on this forum that are way more knowledgeable on this than I am. I was just hoping to kind of ride your coat tails on this subject for my own answers.

NFT (Nutrient Flowing Through) it's a hydroponics technique that has been adapted for aquaponics. Flowing water through tubes with plants suspended above the water level that draw nutrients from the water. 

[Don Cole]

Yes, I have two systems currently one very small 50 gal FT and one 900 gal. FT. I have worms in the small one that have been there for about 5 months. No real noticiable difference at this time with the plants. No worms in the larger one yet as it has only been on line for about a month and a half. I am raising tilapia (30) about 6" long at this point.

[George]

I've run a media system with composting worms for five years and have decided to add a radial flow filter, simply to capture the minute solids which remain suspended in the system.  Also, solids build up in media beds and rafts and I've noticed that many who start with no filtering other than media, later add mechanical filtering - see Bigelow Brook Farm as one example, where the flow was from media to DWC and solids were building up in the raft.

Those planning a new system may as well design in mechanical filtering, if they have room  Any nutrients removed by mechanical filtering can be added back in, if you wish, with a mineralisation step.

Chris, good luck

Don - NFT = Nutrient Film Technique.

[Don Cole]

George,

I stand corrected. I did google the acronym before I posted but google isnt always correct either.

"It was on the internet so it must be true. ;-)"

[Cris Meeks]

Thanks for the info George.  After years of cleaning fish tanks I have to admit that this was sounding just way too good to be true.  Can you please explain what you mean by a "mineralisation step"?

George said:

I've run a media system with composting worms for five years and have decided to add a radial flow filter, simply to capture the minute solids which remain suspended in the system.  Also, solids build up in media beds and rafts and I've noticed that many who start with no filtering other than media, later add mechanical filtering - see Bigelow Brook Farm as one example, where the flow was from media to DWC and solids were building up in the raft.

Those planning a new system may as well design in mechanical filtering, if they have room  Any nutrients removed by mechanical filtering can be added back in, if you wish, with a mineralisation step.

Chris, good luck

Don - NFT = Nutrient Film Technique.

[Jeff S]

I have a 600 gal., (2) 45 gal., and a 100gal systems. The large one has 2 IBC (3 1/2 x 4') grow beds. I also have a swirl filter pre GB to take out a lot of the solids mainly because the tank is very heavily stocked with fish. The worms do a great job breaking down the solids. My nitrates are real high because of low plant count.

I recently cleaned my smaller systems and had no solids build up so I assume the larger beds are the same. The 2 smaller systems have cloudy water and the larger ones are clear. I attribute this to not having any plants in the smaller systems to absorb the nutrients but I'm only guessing.

I also have worm bins that I intend to empty into my soil garden this spring because I've found nothing that grows worms like an aquaponics grow bed. I can easily remove worms from the GBs any time I like. 

[George]

When solids are removed post fish tank, they contain nutrients.  Sometimes those solids are drained to another container and aerated, then allowed to settle and the water is pumped or drained back to the aquaponics system.  This is referred to as mineralisation.  It's a way of removing the nutrients from the solids and keeping them in the system.  

Usually, the solids are drained off the filter and used in soil gardening, especially if the system is heavily stocked and has a nitrogen surplus.  In this situation, there is no concern for keeping all of the nutrients in the system.  

However, when a system is new or lightly stocked, it's important to keep the nutrients in the system.

Cris Meeks said:

please explain what you mean by a "mineralisation step"?

[Cris Meeks]

Jeff, I've seen several comments like yours referring to high nitrate levels in their tanks.  I've always felt that any level over 20 ppm is unacceptable for a healthy fish tank.  I don't hear about water changes very often in this community but I just joined up.  I realize that most of the time you are dealing with very large tanks & that the idea is for the plants to consume the nitrates but when they are not doing that wouldn't you want to take steps to protect the fish and bring down the nitrates?  

Jeff S said:

I have a 600 gal., (2) 45 gal., and a 100gal systems. The large one has 2 IBC (3 1/2 x 4') grow beds. I also have a swirl filter pre GB to take out a lot of the solids mainly because the tank is very heavily stocked with fish. The worms do a great job breaking down the solids. My nitrates are real high because of low plant count.

I recently cleaned my smaller systems and had no solids build up so I assume the larger beds are the same. The 2 smaller systems have cloudy water and the larger ones are clear. I attribute this to not having any plants in the smaller systems to absorb the nutrients but I'm only guessing.

I also have worm bins that I intend to empty into my soil garden this spring because I've found nothing that grows worms like an aquaponics grow bed. I can easily remove worms from the GBs any time I like. 

[Jeff S]

Nitrates don't particularly affect the fish, or so I've been told. Mine seem OK. While water changes shouldn't be necessary with aquaponics when water levels are questionable I don't waste water but use it on compost bins and soil gardens. I should just add more plants and less fish.