Backyard Aquaponics
A place to discuss aquaponics

Hi Jon:

My basement system is set up like what you've drawn up here. The fish tank overflows continuously into a gravel-filled sump tank, and a small continuous pump recirculates that water back to the fish tank. There is a separate sump pump in the sump that can be turned on to pump the sump water up to the outside world (in the backyard). Outside is a "plant sump" that is 70 gallons, with its own pump that runs occasionally on a timer to the plant beds. The overflow for the plant sump is set such that when the water is pumped up to the backyard the plant sump overflows back down to the basement. There is a DIY counterflow heat exchanger on the drain back to the basement to minimize heat loss from the fish tank water. The plants are on their own cycle, which happens much less often than the fish tank's biofilter cycling. Stretch the plants 100 feet up and it'd be the same as your drawing.

I really like having the plants on an independent loop, you can reduce the pumping energy because they aren't as demanding as the fish, and you can tune to the heat of the day or cold night. The fish water can be pumped up to the roof at whatever interval you find convenient. The fish are fine for awhile before needing clean(er) plant water sent back to them.

The only difference I would do would be to collect the solids in a settling area of some sort, and pump the solids up to the roof rather than having them build up in the basement gravel. Over time the basement gravel would become an ineffective biofilter as it crudded up.

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I, too, like the idea of splitting water. One question is how long that would take to clog: I would think it would be very long (at least 5 years, but depends on the amt of waste and whether the ash (fish waste after all carbon has been used up by bacteria, worms, etc) washes out or builds up.

As far as heat loss/gain, I've done some tests and heat loss from a water surface around here with no wind and a significant temperature differential is about U=8 (8 BTU per square foot per hour per degreeF). Heat gain would be less rapid unless one has lots of humidity and cold water so condensation adds heat to the water. Plants would help insulate the channels. I think for accurate numbers you will need to run some tests: reality trumps theory.

Some of the NFT folks here might be able to tell you about nutrients in a mature system. Sure would be nice if they become soluble.

As far as nutrients required: I would figure out the nutrients needed for the roof plants (call some aggie?) and assume that any feed not converted to fish becomes free nutrients. This ignores the fact that fish feed and plant nutrient requirements vary over time and will not always coincide, but should give a good start.

Questions for Steve and Dave:

Why do deeper narrow beds clog faster than shallower beds? Surely as water is moved through the system on the flood and drain cycle things will even out? Whose systems have had problems with cloggin in deep beds?

Why would the solids be needed on the roof. Lets assume that this design uses shallow beds like steve has suggested won't the solids stay in the beds? Isn't that the standard design/procedure/operation of the flood and drain GBs?

I thought that we had thrashed this out pretty throughly way back when I first joined the forum. The way I thought it had been explained to me was that for a given weight of fish you need a certain volume of gravel (for solid processing more than bacteria habitat) and a certain area for planting (to remove nitrates and other nutrients) but how these were laid out didn't matter too much within certain limits (5cm deep gravel for instance would be a bad idea).

The amount of water needed for NFT is pretty minimal so seperating the NFT from everything else would be a good design stratgey.

Whole project sound pretty cool.

DD-
Thanks for your comments, very good to see the practical benefits of this sort of thing, especially with heat gain/loss concerns. Air temperatures swing from -30 C to close to 40C so having good control of when you're exposing the water to even the greenhouse air is critical.

Your sump is full of water correct? Do you think that having a sort of drip system with the occasional flush to move solids around would make it easier to propagate worms? You're right about a bit of solids collection though, if you're going to have any gravel on the roof, might as well use it to deal with some solids. Perhaps also street flora fertilization also. But I think most of the solids handling should be done in the basement so that you can extract some worms ($$$) from the system.

HP- Hopefully be able to design the system so that you don't need to ever clean it out, just harvest the worms every now and again. Ash could certainly be a limiting issue... I think you're probably right that the easiest way to handle this is to do a mass balance on the feed, still though. Perhaps a bit of work there will lead to the answer...

Are there any threads out there that deal with plant grow area vs nitrate increase/decrease with regard to feeding rate? Temps for plant growth probably also play a huge roll....

SC- Only reason to put a portion of solids on roof is because there are plans for some gravel up there (to support bigger plants) and if there's gravel, you might as well squeeze all the solid handling capacity out of it that you can.

Have the same questions that you do on gravel depth...

Stuart I was assuming that the gravel in the basement wouldn't have plants in it just a big biofilter. After a year or so it would be full of stuff that looks and feels just like chocolate mousse.

My gravel beds with loop siphons and no plants accumulated goo over time to where I was getting nitrite spikes as they lost efficiency. If there were plants in it (with a growlight?) then that is another thing.

Correct that there wouldn't be plants in the basement, I was thinking of using worms to deal with the problem of sludge buildup. Any experiences?

Ah, but how did it taste? (Sorry )

Interesting. Did your beds with plants not experience the same buildup? Was the diff due to input rate, worms, or simply to plants being there?



I've found that loop siphons/auto siphons seem to drain incompletely as sediment builds up, leading to anaerobic zones. Perhaps flood/drain would work better for the solids bed as it provides more time to drain completely. If one had a swirl filter (is that correct?) to collect solid waste, one could have a valve that dumps the collected worm feed for several seconds or whatever is appropriate as needed to keep the worms moist and fed. Could be automatic or could be hand-operated once daily.

DJ:
Check out this post on Joel's system: http://backyardaquaponics.com/forum/vie ... rms#p47048

hydro:
thanks for the link, still not sure if it's the plants that deal with solids or the worms...

dave. do you have worms in your sump/filter contraption?

There are some thin reddish worms that were living in the beds (I didn't add them, may have come in with soil) but not enough to be obvious.

I think the difference with Joel's pictures is that is a bed that had plants and worms in it. Maybe you can remove the solids as worm mass, that makes sense, but the excess definitely needs to be removed some way. If you just let a gravel bed collect poo with no removal of plant matter and no removal of worm mass then how would it not become gross? I guess the theory is that the solids become liquid and go to the roof rather than just sit in the gravel? I wouldn't bet on that happening.

I agree that a recessed area in the beds where the siphon hooks up would have helped the beds drain better, but over a year the solids would still settle throughout the gravel if they weren't otherwise removed somehow.

BTW, the chocolate mousse stuff tasted better than expected!

I had the impression that the plants don't remove any solids. From what I've learnt the plants remove nutrients in solution and anything that is in a solid form is unavailable to them. I don't think anyone has posted any research but it seems that the soids are processed by the fauna living within the media.

If your gravel beds were clogging then that impression is either wrong of there is something else going on more likely not going on in the unplanted GBs.

Sorry Dave I didn't finish reading you post before I sent mine. Situations like this that i need the e#$% button.

I didn't think that Joel was harvesting worms from his GBs or at least not on a regular basis or to an extent to account for the beds not clogging with solids.

Could there be another explanation for clogging? Type of food, level of stocking? I ask because if there is not then there must be some other sort of interaction within the GBs that hasn't previously been disscussed on the forum. IF that is the case then a whole bunch of my assumptions on system design are going to be wrong.

Stuart:
Here's how I'm thinking about this mess. The worms take care of the solids. At very low feeding rates (relative to gravel volume), I image that you could do without worms, the solids would be slowly broken down by bacteria. At higher rates, worms are required to digest solids to prevent delicious buildups. In this case, since the scale of the gravel filters will be directly tied to the amount of solids they can remove, I've got to figure out the best ways to promote worm growth.

I imagine they need air, water, space and food. High O2 in the water and low continuous flow (not saturated) take care of the air and water. Harvests (burlap sack on top with some kitchen scraps) would be done to keep the worms from overcrowding and they'd eat as much solids as they could manage. The question is what is the maximum capacity of the gravel to support worms that eat up the solids?

Just a rethink on worms i have a foot deep of worms living under water in my sump see photo and theres thousands of worms liveing in the grow beds so effectivley my system is running on fish waste and worm juce every old plant i pull out has worms and eggs stuck to the roots

I think you are heading down a path that I ventured along. If I didn't annoy a bunch of people with my detailed questions I came very close to it.

The basic answer is we don't know. I can offer two solutions though.

Option 1 do masses of research on worm feeding rates relative to time of year, temps, 02 availablility, density (as a start), calculations to estimate the amount of solid production which will need to include all the vairables affecting your system and them tell us the answer you get bearing in mind that your assumptions had better be spot on.

Option 2 treat the whole system as an ecosytem and vow not to micro manage it. Instead build in redundancy (more gravel, water, less feeding, etc) and it should mostly take care of itself.

Most people on this forum take option 2 and only do things like test their water when something goes wrong and they want to know what so they have a better idea how to fix it. Most peoples systems are so stable that they can get along with a minimum of monitoring without any problems. Jaymie for example still hasn't bought a test kit and until recently had run her system for ages without any problems.

Since option 1 came up in discusion does anyone know what is the minimum dissolved O2 that worms need to survive in water?