Keightley

Mechanical filtration, worms, and ammonia

6 posts in this topic

Posted (edited)

Hi all.  I am new building my first aquaponics system.  I have been posting on other sites and I think I am getting some strange answers to my questions.  Actually the answer at one particular board was quite confrontational.  How dare I overstock my aquarium!  Anyway, this person did raise some questions for me that i thought I would ask here.

If I put worms in my grow bed, do I need to run a biofilter between the grow bed and the aquarium?  Don't the worms eat solid wastes from the fish converting it to a more usable form for the plants?  Also do worms produce ammonia?  If so, is it high enough that I need to take that into account?  Or is it negligible?  

This is what the person stated that made me question whether or not I should use a grow bed as my sole source of removing ammonia and nitrates from the water column.  Before I read this person's reply, I thought that all I would need was my grow bed.  Now I am not so sure.  

Quote

I tried helping a woman on another forum who had a little aquaponics system with 5 fancy goldfish in a 100 gallon aquarium. She had a few grow beds, did regular small water changes in her fish tank, but refused to run a biofilter between the tank and the grow beds. After replacing those goldfish three times, she broke down and built a biofilter. She apparently has been able to keep this last batch of fancy goldfish healthy. 

Maybe the real problem here is that her fish were not producing enough waste to feed the plants?  Or maybe her grow beds were too small for the 100 gallon aquarium?  Maybe it was because she did not include worms in her grow bed?  Or maybe this person is right.  A biofilter ( I am assuming this person means a mechanical filter such as a canister) between the tank and grow bed is necessary in a small aquaponic system. What do you all say?  Is this person right? 

Here are the basics of my aquaponics system.  My aquarium is 200 gallons.  I will be raising fancy goldfish (Lionheads, Orandas, and Ryukins).  The grow bed size I think I have settled on is 96"L x 12"H x 30"D.  I think I can stock the aquarium with 28 goldfish.  Even if these fish grow to record sizes the total pounds of 28 large goldfish will be approximately 28 pounds. Each goldfish will have to reach 12" in length.  But realistically orandas, lionheads, and ryukins will grow to approximately 7 to 8 inches. Six seven inch goldfish will approximately equal one pound of fish. So that means I will have approximately 4.7 pounds of fish.  As I am more interested in the fish than I am with edible plants for this system, I am going to fill the grow bed with tropical house plants. I am thinking pathos and lucky bamboo.   I just cannot image this system producing enough spinach, kale, or basil for me to eat a salad every day.  I hope to one day be in a place where I can have an aquaponics garden that will be able to sustain my family with all the veggies we can consume.  But alas for the time being it shall be a dream of mine.  Afterall, I am still a family of one (well if you include my dog, we are a family of 2)  If anything, I want to learn with this aquaponics set up.  At least the plants will keep the water column clean for my fish and perhaps act as an air filter for my musty basement apartment.  

Cheers!

Edited by Keightley
correcting dimensions of grow bed (see edit history)

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Posted (edited)

Quote

If I put worms in my grow bed, do I need to run a biofilter between the grow bed and the aquarium?  Don't the worms eat solid wastes from the fish converting it to a more usable form for the plants?  Also do worms produce ammonia?  If so, is it high enough that I need to take that into account?  Or is it negligible?

Worms do produce ammonia but it is negligible compared to fish and their effect on microbe ecology will more than compensate from any additional ammonia they produce.

In terms of sizing a media bed take a look at the fact sheet by Dr Wilson Lennard here: http://www.aquaponic.com.au/fact sheets.htm

As to whether you should have biofilter or mechanical filter that depends on a lot of things.  Since your primary interest is the fish I would say if you're media bed is large enough to provide biofiltration you'd still be advised to have a mechanical filter to remove solids.  It's import to understand the different processes that happen in an AP system and which components function to facilitate those processes:

Ammonia production (and introduction of other elements): usually this is done by feeding fish and waiting for them to poop.

Biofiltration (conversion of ammonia to nitrite then nitrite to nitrate): This can by done by a media bed (though it's not as good at doing that as many other methods so it's efficacy depends on size).

Removal of excess nitrates: In aquariums it's usually done by partial water changes and dumping the removed water.  In AP this is normally done with plants although it can also be done with denitrifying bacteria.  The UVI system made use of nets suspended in a tank to host said bacteria and they controlled nitrate levels by controlling the population of these bacteria (hosing off the nets to remove them if they wanted nitrate levels to rise or allowing the bacteria colony to grow if they wanted nitrates to drop).

Mechanical filtration (capture of the solid waste):  Again this can be done by media beds but quite badly.  The disavantages are that the capture is incomplete due to large pore spaces in the media and that with the sludge trapped in the media beds you can't really do much with it, removal is hard without pulling out all plants, and the only mineralization option is worms and a lot of time.  Worms help a lot but do not solve the problem completely.  They still produce waste even if they reduce the volume of it.  Other methods of mechanical filtration are swirl filters, sponge filters, sand beds etc.

Mineralization (extracting further nutrients from captured solids wastes):  Worms do assist in this process.  However if you aren't focused on the plants you might not want to do this at all.  You could simply capture the solid wastes in a mechanical filter and use them to fertilize the garden, compost them or even just discard.

Of course there's always the option of an iAVs sand based growbed which does all of the above very well apart from the Ammonia production.  With a bed the size you're proposing you might be suprised at how much produce you can grow.  But if you're set on a gravel or hydroton growbed I'd at the least have a solids filter in place assuming the gravel surface area is adequate to convert your expected ammonia output. The system may work without one, that depends on a lot of things. But there's no question that with one your fish will be happier, healthier and grow faster.

Edited by Shadders
Had more to say. (see edit history)
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Posted (edited)

Oh wow, thank you for clearing up some of my confusion.  This is FINALLY making more since now.  But I do have a question about the worms.  Can the worms live in the grow bed doing the magic that they do if I have the water mechanically filter through say a canister filter filled with sponges before being placed into the grow bed? Will the worms have enough to eat and flourish?   If not, what would I need to do to make that happen with the water being mechanically filtered before going to the grow bed?  I am reading that there are more benefits to worms than just processing solid fish waste and I would like to take advantage of these benefits: 

1) Worms, in addition to breaking down fish waste, break down excess roots and other materials that plants slough off making them more bio-available to the plants through their excrement: vermicompost. This additional metabolic layer in media based systems is what allow me to avoid the requirement to frequently clean out my grow bed. A 12″ (300 mm) deep grow bed with a healthy population of worms will probably only need to be cleaned out every five years or so, if then.

2) Vermicompost and the corresponding ‘tea’ are tremendously beneficial because they suppress plant disease, suppress plant parasitic nematode, and suppress plant insect pests.

3) Besides helping battle plant diseases, worms have also been shown to mitigate pathogens that affect humans.

4) Worms make a tasty snack for the fish I am raising thus a cheep food source.

Maybe I can have water flow directly from the aquarium to the bed with an external water pump utilizing a solids lifting overflow.  That way some solids, mainly sinking solids such as fish poo, are making it to the grow bed to keep the worms happy and healthy.  And then I can have a separate intake and return for the canister filter which will include the uv sterilizer. I am thinking the canister / uv sterilizer filter would remove floating solids such as fish food, other floates, harmful bacteria and virus. Maybe a fluidized sand bed would be the way to go here instead of a canister filter?  If the canister or fluidized sand bed filter is the way to go, would I return the water from the canister/fluidized sand bed directly back into the aquarium or would I return the water to the grow bed? 

Thanks again for your thoughts and comments.  I really do appreciate them more than you can possibly imagine.

Cheers,

Keightley

Edited by Keightley
adding another thought (see edit history)
Shadders likes this

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Hi Keightley

Welcome to APN/HQ

If the growbeds are kept so clean that the worms won't survive in them, the fish will be really happy.

You should read AquaAuroras threads she is keeping goldfish in aquariums indoors

here:

and here:

cheers

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Hi Shadders

Welcome to APN/HQ

Nice first post :thumbsu:

Keep up the good work :)

 

9 hours ago, Shadders said:

 

Worms do produce ammonia but it is negligible compared to fish and their effect on microbe ecology will more than compensate from any additional ammonia they produce.

In terms of sizing a media bed take a look at the fact sheet by Dr Wilson Lennard here: http://www.aquaponic.com.au/fact sheets.htm

As to whether you should have biofilter or mechanical filter that depends on a lot of things.  Since your primary interest is the fish I would say if you're media bed is large enough to provide biofiltration you'd still be advised to have a mechanical filter to remove solids.  It's import to understand the different processes that happen in an AP system and which components function to facilitate those processes:

Ammonia production (and introduction of other elements): usually this is done by feeding fish and waiting for them to poop.

Biofiltration (conversion of ammonia to nitrite then nitrite to nitrate): This can by done by a media bed (though it's not as good at doing that as many other methods so it's efficacy depends on size).

Removal of excess nitrates: In aquariums it's usually done by partial water changes and dumping the removed water.  In AP this is normally done with plants although it can also be done with denitrifying bacteria.  The UVI system made use of nets suspended in a tank to host said bacteria and they controlled nitrate levels by controlling the population of these bacteria (hosing off the nets to remove them if they wanted nitrate levels to rise or allowing the bacteria colony to grow if they wanted nitrates to drop).

Mechanical filtration (capture of the solid waste):  Again this can be done by media beds but quite badly.  The disavantages are that the capture is incomplete due to large pore spaces in the media and that with the sludge trapped in the media beds you can't really do much with it, removal is hard without pulling out all plants, and the only mineralization option is worms and a lot of time.  Worms help a lot but do not solve the problem completely.  They still produce waste even if they reduce the volume of it.  Other methods of mechanical filtration are swirl filters, sponge filters, sand beds etc.

Mineralization (extracting further nutrients from captured solids wastes):  Worms do assist in this process.  However if you aren't focused on the plants you might not want to do this at all.  You could simply capture the solid wastes in a mechanical filter and use them to fertilize the garden, compost them or even just discard.

Of course there's always the option of an iAVs sand based growbed which does all of the above very well apart from the Ammonia production.  With a bed the size you're proposing you might be suprised at how much produce you can grow.  But if you're set on a gravel or hydroton growbed I'd at the least have a solids filter in place assuming the gravel surface area is adequate to convert your expected ammonia output. The system may work without one, that depends on a lot of things. But there's no question that with one your fish will be happier, healthier and grow faster.

 

cheers

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Can the worms live in the grow bed doing the magic that they do if I have the water mechanically filter through say a canister filter filled with sponges before being placed into the grow bed? Will the worms have enough to eat and flourish?

Quote

1) Worms, in addition to breaking down fish waste, break down excess roots and other materials that plants slough off making them more bio-available to the plants through their excrement: vermicompost

I put these quotes together to demonstrate that their will in fact be food available for the worms.  Worms have a marvelous behavioral property in that they will self regulate their biomass to match the food supply.  If there's not enough food worms will actually shrink (and some may die providing food for the other worms).  If there's more than they need they grow larger and make more baby worms.  So yes they'll probably still flourish, but if there's less food not in as high a numbers.  One thing to remember is solids filters are not 100% efficient.  I think swirl filters and settling tanks acheive about 60-70% efficiency (if memory serves me correctly). Finer sponge filters after this stage can increase it higher.

Quote

1) Worms, in addition to breaking down fish waste, break down excess roots and other materials that plants slough off making them more bio-available to the plants through their excrement: vermicompost. This additional metabolic layer in media based systems is what allow me to avoid the requirement to frequently clean out my grow bed. A 12″ (300 mm) deep grow bed with a healthy population of worms will probably only need to be cleaned out every five years or so, if then.

2) Vermicompost and the corresponding ‘tea’ are tremendously beneficial because they suppress plant disease, suppress plant parasitic nematode, and suppress plant insect pests.

3) Besides helping battle plant diseases, worms have also been shown to mitigate pathogens that affect humans.

4) Worms make a tasty snack for the fish I am raising thus a cheep food source

I can't argue with the benefits of worms (that's why I'm planning to build a fishless system powered by worms) but they are primarily benefits to plants.  Although I might argue with point 4.  Worms are actually extremely valuable, they retail for about $100/kg in Queensland.  Fish feed is a lot cheaper.

But since we are now talking about primary benefits to the plants that changes things somewhat.  You've stumbled , quite quickly, upon the inevitable truth of AP which is that it is a compromise.  What's ideal for plants is not always ideal for fish and vice versa.  There is some symbioses (the nitrification cycle and the fact that both like well oxygenated water) which arguably is what makes it worthwhile.  But in many other cases there is a conflict of interest that must settled by compromise.  e.g. Plants typically prefer a lower pH than fish.  Plants would prefer as much fish poop swimming around the system as possible, fish would prefer none.

I can't recall the exact numbers but solid fish waste still contains something in the region of 70-80% of the fish feed nutrients in a non-bioavailable form.  What do with those wastes is one of those compromise decisions.  If you want ideal conditions for fish, take the wastes out of the system (They can still be used usefully outside the system).  If you want ideal conditions for plants, keep them).  If you want the best of both worlds get as much nutrient out of them as possible and keep them away from the fish as much as possible. This is where mineralization comes in.  And quite rightly you point out that worms are one way to achieve this (and provide a number of other benefits in the process).  There are also other methods of unlocking those nutrients (google offline mineralization).  Bluesmart Farms send their solid wastes (along with some water) on a separate circuit to a dedicated worm bed then return the water after the worms have done their work and made most of the solid waste nutrient into a bioavailable/soluble form.   This adds complexity to the system but appears to be an effective mechanism.  The system is described in fair detail in their patent here: http://www.google.com/patents/US20100031893 .  Don't get me started on the patent though.  Basically they've added worms in a separate bed and tried to patent aquaponics :angry:

In order to work out the best way for you go it would probably be useful to clarify some points.

1/ Are you prepared to remove up to 80% of fish feed nutrients and accept the consequent loss of plant growth? If yes, then a solids filter between fish tank and growbed, dump the waste on the garden.  You can still have worms but their population will be smaller.  This is the option that provide for best water quality for fish with the simplest build.

2/ If not, are you prepared to add complexity to the system?  If yes then as above but put the solids from the filter into a dedicated flood and drain worm bed and return the water to the system periodically.  You can also recycle plant wastes in the worm bed.  Instead of a worm bed you could use offline mineralization (which is simpler) but you want the benefits of the worms so this is an option.  Alternately consider a dual loop system.

3/ Are you prepared to compromise on water quality for a simpler build and better plant growth?  If so then a simple system with worms, no solids filter, but a ratio of fish to plants biased in favour of the fish (less fish more plants/growbed).

4/ Are you you married to the idea of a gravel/clay ball grow bed?  If not look at iAVs sand beds.  Very simple build, maximises nutrient extraction, plant yield, solids filtration and biofiltration. The only downside I've seen so far is that sand beds are about double the weight of an equivalent sized clay ball bed.  To my knowledge no one has experimented with worms in an iAVs system though.  I might be the first, unless you beat me to it.

One last thing.  Be careful using a UV sterilizer. I'm not sure what you want to sterilize but AP relies on bacterial populations.  It will sterilize the beneficial bacteria as well.

ande and Keightley like this

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