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I've seen a few discussions about small AP systems and why they wouldn't work.  How could one be designed that would work?

I'm thinking something like 3 gallons fish-tank.  For a 2:1:0.5 rule of thumb, the system would need 6 gallons of grow bed, 3 gallon fish tank, and up to 1.5lb of fish.  Basically, put a full grown 1.5lb plate ready fish into a 3 gallon tank and hook it up to a 28qt storage bin for a grow bed.  The image this brings to mind seems absurd.

I remember seeing an article about pond filters.  The premise was to compute the rate that ammonia is produced by the fish (based on how much they are fed), the ammonia that is consumed by the bio-filter, and the water retention time in the bio-filter.  The target is to make sure that the bio-filter can consume ammonia at a rate at least as great as the rate the fish produce it, and that the water is retained in the bio-filter long enough for the bacteria to do it's work.  Is this basically what is needed to design a suitable system?

Dave

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Jesse - the 10 minute of water retention in the bio-filter is from the cited article.

This is great information.  If it is taking 10 minutes to flood the grow bed, then 10 minutes to drain, then on average the water retention is 10 minutes.  The flood period provides 5 minutes, the drain period provides another 5 minutes.  I was assuming the drain would be instantaneous; which of course, it isn't (silly mathematician).  As long as the flood and drain takes a total of 20 minutes, then it'll have 10 minutes of water retention.  So flood more slowly and drain faster still works for ammonia consumption by the bacteria.  I have no idea what it does to the plants except what you tell me.

Of course, your experiments mean more than some article I found on the web.  Besides, I'm not even using the article for it's intended purpose (filtering large koi ponds).  It just gives me some equations to work with and make predictions to test whether it's close enough.  What happens if the flood and drain cycle takes a total of 5 minutes or less?  Does this still filter the ammonia properly?  I hear that auto-siphons aren't perfect at draining the water.  How much water is retained after each drain?

Dave


Jesse Hull said:

You want the flow through rate to be @10 minutes on settling filters to allow time for things to sink and some biofilters if there's adequate aeration within the biofilter chamber.  

Consider that when media beds are your biofilter, and it takes 10 minutes to flood, the lowest roots are underwater and may not be getting enough oxygen for a longer period of time.  If it takes also takes 10 minutes to drain, that's probably too long (in this case, 10 minutes is the maximum).  Roots will alter to compensate to a point, and it's not that the plants won't grow or even thrive, but the best conditions are made by an aerated quantity of water, a constantly flowing aerated water column, or a quick flood and drain.

I did many tests with hydro-organic systems in the past using biofilters.  At later stages in the trials, I actually started pitting ebb/flow, aeroponic, and NFT against each other.  I was able to achieve as good or better results in ebb/flow by using a bigger pump and larger drain fittings, and more frequent waterings... quick flood, quick drain, exchange nutrient levels more often.  The quick flood meant that nothing was under water for too long a time, and the quick drain drew air into the spaces that were previously filled with water.

Seriously, I had no idea...

Tilapia are Chichlids

Tilapia The most important food cichlids, however, are the tilapiines of North Africa. Fast growing, tolerant of stocking density, and adaptable, tilapiine species have been introduced and farmed extensively in many parts of Asia and are increasingly common aquaculture targets elsewhere.

David,

Yes I have small setup in my kitchen. Photos should be under my profile for you to view

20 Gallon Aquarium no media on tank bottom

10 Gallon tote bed fill and drain, venturi bell siphon 12" deep, Venturi drain aeration with 12" drop.  Fill rate of 13 minutes - drain 30 seconds

5 Gallon trough bed constant fill 1/2 full. 4"x 4" x 6'. Constant drain no aeration to tank

4 Comet Goldfish ranging is sizes from 2" to 6" (most around 4-5")

475 gph Statuary pump with 5 foot lift with a "T" feeding two beds (Final rate at top is app. 30 gph)

7" disk aeration plate on bottom of tank

Feed fish at least 2x's a day.  High protein vegetable flakes and a pea/spinach/green bean pellet (home made)

1lb red worms in 10 gallon tote, 30-40 red worms in trough.

All tubing is 1/2 cpvc on the water inlets to keep pressure, drains are 3/4" pvc reduced to 1/2" to 3/4" for venturi.

Fish waste is not a problem, the pump sucks up most.  Once a week I hit the bottom with a hand vacuum to get under pump.  Solids go to a jug and get dumped right into the beds.  Takes all of 1 minute to do.  The fish have learned that occasionally a worm comes out the drain and they now sit there waiting for a treat.

During my time at a hatchery all tanks would have all water exchanged every 3 hours.  Tanks ranged in size from 1200 gallons to 20,000 gallons,  All tanks were cylindrical with a solids drain at the bottom draining to a waste tank.  Waste was then pumped into large IBC's and delivered to farmers for mixing with fertilizer.  Pumps we used were all rated for 3000 gph and then adjusted down for lower flow.  Some tanks had less exchange depending on species.  Example Trout water would change every 3 hours.  Bass, Gar, Sturgeon and Bullhead would exchange 1 time a day,  Waste would flow out constantly just on gravity and tank design.  The only filters we used outside of a biofilter from the tanks was at the inlet to the tanks,  These were large charcoal canisters that would finish cleaning the water before it entered the tank.

If you are looking for the aesthetics of a fish tank with gravel, you are still going to have some of the maintenance you normally have with an aquarium.  If there are worms in the fish tank, the fish will find them, regardless of species. Chichlids are notorious diggers.  You might be able to find a statuary pump with an external filter line to adapt to an under gravel screen that will suck up solids from under that plate, I just have not seen those screen in years.  Tetra has such a filter but you need to buy the external filter separately and it will not effect its ability to pump above gravel.

Worms - they can be ferocious eaters and they will self control their populations in a growbed.

Now my problem is the plant part but the fish and the fish tank are working wonderful.  Had my pitfalls getting it cycled but Vlad and TCLynx as well as Phil provided some tips to help me get it cycled.

If you are that interested in the math, I would really suggest you do some reading on Biometry.



David Palmer said:

John, it's wonderful to have your input on this!  As noted, I'm just a math guy with just enough information to be dangerous. 

Certainly each fish has it's own characteristics.  The idea is to work through the most important factors and provide guidance for smaller systems of 30 gallons or less.   This is not for producing fish to eat, but having pets that help grow basil.  Goldfish should not be recommended for this purpose as they can grow up to 12" in length.  Maybe small Chichlids would be good (http://en.wikipedia.org/wiki/Cichlid).  What other fish would be good?

I did some extra calculations and found a contradiction that suggests the math I'm doing won't work as stated. Something else is needed or the fish will die.

Lets consider the rule of thumb requiring 2 gallons GB to 1 gallon FT to 0.5lb of fish.  People providing this information aren't stupid - they know that if you exceed this rule of thumb, things are likely to go bad.  Meaning, fish will die.

Lets say that we have the worst possible media, smooth stone at 70:1 SSA.  For each gallon of grow bed, I get an ammonia consumption at 0.26 grams/day.

The highest feeding rate from my source document suggests 3% of the fish weight (farms want to fatten them up, maybe they provide more food than this?).  Thus for each 1lb of fish, we're feeding them 13.6 grams of food/day.  This then produces 0.5 grams/day of ammonia.

So, how many fish can the grow bed bio-filter support?  I'm coming up with 0.75lbs per 1 gallon of grow bed.  That's a bit much.  Especially when you consider that the recommended density is 0.5lbs per fish tank gallon.  In other words, we're stocking at 1.5lbs of fish per every 1 gallon of fish tank!  What a breakthrough! 

Clearly something is wrong with my assumptions.  From what I've read, aquaculture farmers spends a lot of time removing fish solids from their tanks.  The cited source on the bio-filter even notes that a pre-filter is required for the bio-filter.  This pre-filter is needed to remove fish solids.  Without removing them, we have another waste input that isn't being address, thus leading to fish deaths.

What can be done about fish solid waste?  1) use a siphon to remove it every week, or 2) grow worms.  Certainly the siphon is what aquariums normally use as the bio filters for pet fish don't process solids.  You can get special under-gravel filters so that you can remove the solids.  I really hate doing this.  But if the solids aren't removed, then I expect the fish will die.

The second option is to add worms.  Not any old worm, but composting worms - like red worms or tiger worms.  I just went to my compost pile and dug some up.  I don't use manure in the compost pile, so it should be clean of e-coli.

But another equation is needed here.  How much solids do the fish produce?  How quickly can worms consume the solids?  What is the maximum worm-holding capacity for a given container?  I don't know... do you have a reference to an article to aide in my education?

I have two options of where to put the worms: I can put them in the pea gravel at the bottom of the fish tank or in the grow bed.  Goldfish like to dig.  I suspect he'll find the worms if they are in the pea gravel.  However, in the grow bed, the worms would have plenty of room.  They will reproduce until the worm population is able to consume all of the fish solid waste. But then I need to remove the pea gravel and replace it with sand.  This is to make sure the solids don't get trapped in the gravel and can get sucked up by the pump and delivered to the grow bed.

Hopefully the guy with his kids school experiment drops in.  I could run some numbers to see what kind of setup is more likely to survive if my assumptions aren't too far off the mark. 

Do you have a small AP setup?  Please post the details so I can check to see if this meets with the theory.

Thanks for the info John!

I tried finding the SSA for hydrocorn.  The best I could find is the paper, "Physocichemical properties of motrmorillonite interlayered with cationic axyalminum pillars" by M. L Accelli and R.M. Tindwa in 1983, The Clay Minerals Society.  They found that "...polymers appears to have produced an expanded clay with surface area of 200-300 m^2/g."  I found a post in an aquaponics discussion claiming that a 50 liter bag of hydrocorn weighs 49lbs.   That's 444.5 kg/m^3.  Converting to m^2/m^3 gives an astronomical SSA. 

Basically, if you are using hydrocorn, then you have plenty of room for bacteria to grow.  Be more concerned about water retention time and how many fish can comfortably fit in the 20 gallon tank. 

Why do you have 4 fish?  Could you maybe put 8 fish (1 fish per 2.5 gallons) in there and expect it to work well?  What limits the fish density for your system? 

Dave


John Cubit said:

David,

Yes I have small setup in my kitchen. Photos should be under my profile for you to view

20 Gallon Aquarium no media on tank bottom

10 Gallon tote bed fill and drain, venturi bell siphon 12" deep, Venturi drain aeration with 12" drop.  Fill rate of 13 minutes - drain 30 seconds

5 Gallon trough bed constant fill 1/2 full. 4"x 4" x 6'. Constant drain no aeration to tank

4 Comet Goldfish ranging is sizes from 2" to 6" (most around 4-5")

475 gph Statuary pump with 5 foot lift with a "T" feeding two beds (Final rate at top is app. 30 gph)

7" disk aeration plate on bottom of tank

Feed fish at least 2x's a day.  High protein vegetable flakes and a pea/spinach/green bean pellet (home made)

1lb red worms in 10 gallon tote, 30-40 red worms in trough.

All tubing is 1/2 cpvc on the water inlets to keep pressure, drains are 3/4" pvc reduced to 1/2" to 3/4" for venturi.

Fish waste is not a problem, the pump sucks up most.  Once a week I hit the bottom with a hand vacuum to get under pump.  Solids go to a jug and get dumped right into the beds.  Takes all of 1 minute to do.  The fish have learned that occasionally a worm comes out the drain and they now sit there waiting for a treat.

The trough of 4" x 4" x 6' is about 5 gallons.  At 30 gph, your water retention time is about 10 minutes.  This is spot on for the pond recommendation.

How did you weight just the worms in the 10 gallon tote?  Did you add 30-40 red worms in the trough?  Not 1/2 lb?

It was the way I purchased them.  I had a purchased an additional 1lb of worms and the 30-40 came from my existing worm bin.  Technically 5 gallons is media and water.  I recently drained it and it really only held 2 gallons filled (with media) and I keep it at 1/2 full so really only 1 gallon of water is in it at a time.

David Palmer said:

The trough of 4" x 4" x 6' is about 5 gallons.  At 30 gph, your water retention time is about 10 minutes.  This is spot on for the pond recommendation.

How did you weight just the worms in the 10 gallon tote?  Did you add 30-40 red worms in the trough?  Not 1/2 lb?

Hydrocorn by far has more surface area than hydroton.  The inconsistent size and shape seems to work well for water retention, but under lights it seems to dry out faster on the surface.

I started with 10 fish.  I had a bad ammonia, nitrite swing that killed off 6 of the.  The current number is just what is left.  I am holding off on adding more as 3 of those fish have all doubled in size in 3 months.  Remember you need to assume what the final size and weight of the fish will be not what it is as you put them in the aquarium.  If they have the potential to grow another 3-6 inches to 9-12 inches in size, I have to assume the final would be 12".  High density stocking is tricky on the aquarium end like ours is.  You do not have rotating stock and you are not moving fish to other tanks based on the size. If you were raise fish for food or sale then your would start with the HD Stocking then thin down as the grow, moving largest to one tank say all 9-12", next tank would be all 6-11" and the last tank would be 2-6".  The smallest could be considered nursery stock till they grow.  In return you would eat or sell those in the largest size, get breeders from you mid size.  Waste factor is usually the largest produce the most nutrients (waste).  Example one rainbow trout at 12" can produce the same amount of waste as 400 fingerlings or 1000 fry.

In my current setup nutrients are not the current problem, what I am seeing usually in the death of plants is a result of fungus (Thanks Vlad for the tip) from excessive water. I may have a minor problem with trace minerals and with some Maxicrop I will see if that changes.

David Palmer said:

Thanks for the info John!

I tried finding the SSA for hydrocorn.  The best I could find is the paper, "Physocichemical properties of motrmorillonite interlayered with cationic axyalminum pillars" by M. L Accelli and R.M. Tindwa in 1983, The Clay Minerals Society.  They found that "...polymers appears to have produced an expanded clay with surface area of 200-300 m^2/g."  I found a post in an aquaponics discussion claiming that a 50 liter bag of hydrocorn weighs 49lbs.   That's 444.5 kg/m^3.  Converting to m^2/m^3 gives an astronomical SSA. 

Basically, if you are using hydrocorn, then you have plenty of room for bacteria to grow.  Be more concerned about water retention time and how many fish can comfortably fit in the 20 gallon tank. 

Why do you have 4 fish?  Could you maybe put 8 fish (1 fish per 2.5 gallons) in there and expect it to work well?  What limits the fish density for your system? 

Dave


John Cubit said:

David,

Yes I have small setup in my kitchen. Photos should be under my profile for you to view

20 Gallon Aquarium no media on tank bottom

10 Gallon tote bed fill and drain, venturi bell siphon 12" deep, Venturi drain aeration with 12" drop.  Fill rate of 13 minutes - drain 30 seconds

5 Gallon trough bed constant fill 1/2 full. 4"x 4" x 6'. Constant drain no aeration to tank

4 Comet Goldfish ranging is sizes from 2" to 6" (most around 4-5")

475 gph Statuary pump with 5 foot lift with a "T" feeding two beds (Final rate at top is app. 30 gph)

7" disk aeration plate on bottom of tank

Feed fish at least 2x's a day.  High protein vegetable flakes and a pea/spinach/green bean pellet (home made)

1lb red worms in 10 gallon tote, 30-40 red worms in trough.

All tubing is 1/2 cpvc on the water inlets to keep pressure, drains are 3/4" pvc reduced to 1/2" to 3/4" for venturi.

Fish waste is not a problem, the pump sucks up most.  Once a week I hit the bottom with a hand vacuum to get under pump.  Solids go to a jug and get dumped right into the beds.  Takes all of 1 minute to do.  The fish have learned that occasionally a worm comes out the drain and they now sit there waiting for a treat.

Wow! im out.... please post some pics when your done with your project.

I am a little late to the discussion I think, but we have been running and building micro systems for the past 18 months and have honestly had no issues at all with them.  We check the water a few times a week, keep stocking densities very low, just use small goldfish, and are growing a variety of plants - one system has just small houseplants in, and the other we had strawberries, lettuces and herbs.  All did really well.

We submitted our IKEA-based micro aquaponics design to several DIY sites (Instructables / Wikihow / Make:Projects) so that others could make these systems as well - and the reports have been really positive so far and I am happy that new people are getting involved and trying out aquaponics: we also put the instructions on our own site as well:

http://www.japan-aquaponics.com/micro-aquaponics-plans.html

This is also another link to our wooden micro system that we currently have running in our living room - I need to update the photos showing the plants - but will do that tomorrow I think!

http://www.japan-aquaponics.com/black-micro-aquaponics-system.html

Hope that these examples are good for you, and the small systems really can work as long as they are set up carefully, looked after nicely, and monitored regularly to make sure that nothing toxic is building up.

All the best,

Aragon

Aragon,

You have plenty of great information on your web site!  I've seen those designs before on Instructables, but I hadn't seen the web site.

Let's run some numbers...

If we take an example starting point of a 1000 litre fish tank, with 2, 500 litre growbeds positioned above the fish tank. Water will be pumped from the fish tank 50cms up to the growbeds, and will then directly return to the fish tank via the outflow pipes in the growbeds. Assuming that we are running the pump constantly then it needs to be powerful enough to move at least a 1000 litres of water 50cms high in 1 hour.   However, if you are planning to run a timed flood and drain system, then you need to allow for the fact that the pump may only be on for 15 minutes every hour. If this is the case then the pump needs to still move the entire volume of the fish tank - but it needs to do it in only 15 minutes... and so you will need to use a much more powerful pump to allow for this. In this case the pump would need to be able to move at least 4000 litres of water to a height of 50cms in 1 hour.

In this case, you have the grow bed is the same size as the fish tank (GB is two 500 liter tubs, FT is 1,000 liters).

Lets start with the constant flow design:

* pump moves FT to GB once every hour

* overflow lets water go back from GB to FT

* GB is filled with grow media, thus only 50% of the volume is available for water (1/2 FT)

retention time = volume / pump rate

retention time = 1/2 FT / (FT/hour) = 30 minutes

I don't need to worry about SSA as there is plenty of room for most any media to grow more than enough bacteria to consume ammonia being produced.

For the flood-and drain mechanism, there is a change if pump rate.  It needs to move the entire FT volume in 15 minutes (1/4hour).  Then it slowly drains the water for 45 minutes (3/4 hour).

retention time = 1/2 * (volume * pump rate + volume * drain rate)

retention time = 1/2 * (1/2 FT / (FT /  15 minutes) + 1/2 FT / (FT / 45 minutes))

 = 1/2 * (1/2 * 15 minutes + 1/2 * 45)

 = 1/2 * (7.5 minutes + 22.5 minutes)

 = 1/2 * (30 minutes)

 = 15 minutes

The short version for any fill and drain is that the retention time is simply 1/2 the cycle time.  The cycle time is the time between starting each flood.  This applies to auto-siphons, ebb and flow, and timed flood and drain systems.  They are all based on putting water in, then letting is come out.

What I find interesting is that the advice is to have well over the 10 minute of retention time recommend in the pond bio-filter document.  This is great news.

I picked up a book on Koi ponds that reaffirms this recommendation.  It suggests a bio-filter of at least 1/3 the pond size (or 1/2 FT), and to pump the entire pond water through it once every 2 or 3 hours.  They always use constant flood.  This gives a retention time of (1/3 FT) / (FT / 2 hours) = 40 minutes.  Elsewhere in the book, they recommend a minimum of 10 to 15 minute retention time.  I now have multiple sources advising a retention time of at least 10 minutes.


Japan Aquaponics - アクアポニックス 日本 said:

I am a little late to the discussion I think, but we have been running and building micro systems for the past 18 months and have honestly had no issues at all with them.  We check the water a few times a week, keep stocking densities very low, just use small goldfish, and are growing a variety of plants - one system has just small houseplants in, and the other we had strawberries, lettuces and herbs.  All did really well.

I'm curious about the micro-aquaponics system.  From the article, there are 20 fish in a small tank with a 13 liter grow bed filled with lava rock (SSA of 282:1). 

* what is the volume of water in the fish tank?

* how fast is the pump?

* how many grams of food do you feed the fish each day?

From looking at the pictures, it's clear that this system does not follow the rule of making the grow bed the same volume as the fish tank.  Thus I'm concerned about the amount of bacteria the grow bed can maintain.  How long have you run it like this?  What do the water tests show for pH, ammonia, nitrites, and nitrates?

Japan Aquaponics - アクアポニックス 日本 said:

This is also another link to our wooden micro system that we currently have running in our living room - I need to update the photos showing the plants - but will do that tomorrow I think!

http://www.japan-aquaponics.com/black-micro-aquaponics-system.html


David, you are going to get really board with aquaponics when you get past all the math, and get on to the "just feed the fish twice a day" part. ...there is just not that much to it, and youre over thinking it for sure.

try to just read the aquaponic books, and not the pond, and aquarium books.

aquaponics has its own set of rules at this point, focus on the basics of design and function, and skip the math involved with bio filter capacity etc. ...build a system already!

..here i go again, barking at the neighbors before i have had my first cup of coffee.

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