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PostPosted: Mar 14th, '18, 06:09 
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Hi!
New guy here, planning my first aquaponics system. I've done plenty of reading but haven't built anything yet.
The system I'm planning is a media bed, flood and drain system using about a 450 gallon (US) fish tank. I live in coastal British Columbia where our typical winter temperatures are about 5 to 10 Celsius (say 40 to 50 degrees F) but can be as low as -5 to -10C for short periods. I'm planning to use rainbow trout and keep the water as close to 15C (60F) as I can, year round.

My proposed arrangement is:

1. Conical bottom fish tank set in the ground (to moderate the temperature year round).
2. Submersible pump in centre of the fish tank
3. Pump pumps up to an MBBR
4. Outlet of MBBR by gravity to media beds
5. Outlet of media beds by gravity back to fish tank

So to finally get around to my question: is there any reason or need to have a radial flow separator or other pre-filter before the MBBR? Most systems seem to have them, and I get that they would be a necessity for a deep water culture or NF type system.
The reason for the MBBR is just to jump start the nitrification - I'm concerned that winter temps will be too cool in the media bed to rely just on it for nitrification. I'm thinking that the submersible pump will chop up the larger solids and the agitation of the MBBR will also help to break them up, and then they will flow through to the media bed for mineralization.
Any problems that you see with this?
Thanks in advance for all assistance!


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PostPosted: Mar 14th, '18, 09:51 
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The short answer is yes this will work. I'm scratching my head and asking why you would want to keep the grow beds connected if they are going to be pulling the temperature down enough that they won't function as a biofilter when you're keeping the water at 60 degrees? I get that you need them for solids filtration but you might also be able to do something like my suggestion below.

If you design it with a top outflow, floating media and a way to flush out trapped solids you can run the Moving Bed BioReactor as a Static Upflow Filter part of the time to get rid of some solids.

These aren't specific to your question but might help with some additional information that could be useful to you -

http://www.lagazzettadellekoi.it/wp-content/uploads/2017/03/MBBR.pdf

https://cals.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop%20PP%20%20&%20Misc%20Papers%20Adobe%202006/7%20Biofiltration/Nitrification-Biofiltration/Biofiltration-Nitrification%20Design%20Overview.pdf


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PostPosted: Mar 14th, '18, 13:35 
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Thanks for your response.
I'm not sure I understand your question, though - "why would I want to keep the growbeds connected"? Well, to grow food in of course.
As I understand it, nitrifying bacteria will function at 60 degrees but only at about half the rate as they would at 80 degrees. So logically, you'd need twice the biofilm area for a cool water system compared to a warm water system. (A local commercial operator with a DWC system confirmed that for me too). Hence the MBBR to supplement the bacteria in the grow beds, not replace them.
Plus, I'm planning to have the fish tanks and MBBR in an insulated shed that I can heat during cold snaps. There will be heat to the greenhouse too but obviously it is going to be harder to keep that warm.

There is very little information around on cool water aquaponics systems so I'm trying to make intelligent guesses about what will work. What information that is out there, like the 2 links you mention, is usually for recirculating aquaculture which has more in common with municipal sewage treatment where the goal is simply to remove solids out of the system as quickly as possible. Then convert the ammonia to nitrates because they are less toxic and can be removed by water replacement. Since their goals are different from mine, I can't assume that their methods are ideal for my needs.

Thanks for the suggestion about the Static Upflow Filter - I'm going to consider that.

Also, there was one potentially useful bit of information in the second link you provided: apparently if there are high organic loads in a filter system then the heterotrophic bacteria can outcompete the nitrifying bacteria. Sounds like I need to do a bit more research on that.


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PostPosted: Mar 14th, '18, 20:56 
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Good morning Gabriola
Welcome to this forum.
Our system here in northern New Mexico, while in a earth-sheltered greenhouse runs water in Winter at 56F. We also run a MBBR to add more biological surface area. I hadn't noticed nitrite levels to nitrate levels fluctuate during Winter. Seems like I need to do more logging to learn more about this concern and thank you for bringing this issue forward.
I've been considering doing something similar with our outdoor Koi pond system where I can take the outdoor grow-beds off-line during Winter. I'll be following this to see what you come up with.
Brian

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Specs: 2600 gallon (347.56cf) FT. 44cf GBs. 200 gal (26.7cf) ST. 15 gal (2cf) RFF. 50 gal (6.7cf) biofilter.
2017 season 100 Brook trout fingerlings. 5 Comets.
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PostPosted: Mar 15th, '18, 04:37 
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What I didn't know with your grow beds was that they will be in a greenhouse so there won't be that much heat loss.

Grow beds work well as heat exchangers - my unheated system with 625 gallon fish tank and about 1000 gallons of water total, can often gain or lose about 6 degrees F a day. My question was basically why pay to heat water to 60 degrees during winter, only to lose that heat every time the water passes through the cold grow bed. That's what made me think, why not just setup a Recirculating Aquaculture System (RAS) with the ability to run some grow beds during the growing season (so you only have to heat the RAS in winter, not the grow beds). If you want to grow much during the winter as far north as you are, you will have to provide supplemental lighting as well. You probably already knew this but I thought I'd throw it out there - anything under about 10hrs of light per day is a problem if I remember right. Here's a link that talks about the light issue - http://www.waldeneffect.org/blog/When_to_plant_for_a_winter_harvest/

Heterotrophs aren't usually a problem, yes they are present and have an affect but unless you're throwing way too much at your grow beds you should be OK. I'm not really sure that you need to have an MBBR but if you're planning to run high fish loads for the number of grow beds you have then it's probably a good idea. High fish loads require more maintenance and you may have to clean out the grow beds as well. If you go with high fish loads then putting some solids filtration before the grow beds is a good idea (Like a Radial Flow Filter, Drum Filter, Sieve or Static Upflow Filter). If you want to reclaim the nutrients in those solids, you can either put them out into your garden or compost them or you can setup a mineralizer in your system and feed the nutrients back into the system. You can also just put a portion of them into the grow beds and use the rest elsewhere.

FYI - I run a cold water system which is mostly unheated in winter ((heated when water gets below 40 F). I eventually hope to shift back to trout but don't plan on heating the water (might have to cool it a couple of times each summer though). Right at the moment I'm having fun growing catfish and bluegill which are warm water fish and don't eat that much in the winter so additional filtration during winter isn't an issue.

- Cold water also makes it less likely for ammonia to be in the toxic form (See chart here - http://ibcofaquaponics.com/information/tables-and-charts/).

If you haven't looked at it yet the IBC of Aquaponics is a good read - link to free PDF in the upper right corner of the BYAP page you're looking at. Straight grow bed systems no other type of filtration so it won't help you with your filtration questions but more of interest to see other peoples systems.

Cheers


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PostPosted: Mar 15th, '18, 11:23 
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Thanks again, both of you.

Guess I should have mentioned the greenhouse. One of the main goals of the system is to have fresh veggies in the winter.

Scotty, you read my mind about the heat exchanger issue. Keeping a fish tank heated or cooled is one thing, but how much will the temperature be affected by flooding and draining the grow bed? And a closely related question is how will the nitrifying bacteria react to being repeatedly exposed to cold air, then doused in relatively warmer water? That is another reason for the MBBR - a backup in case the bugs don't like the cold air in the grow beds. I don't expect that anyone can answer those questions precisely for my given setup so I'm planning to log hourly temperature data - fish tank temp, ambient outside temp, ambient greenhouse temp and return water temp from the grow bed (I'm an engineer and I like data...). Then use that data to figure out what is the most efficient way to keep the system running with the minimum amount of energy input.

I'll be starting out with a low stocking density at first, hopefully increasing it as I learn what I'm doing.

And yes I'll need supplementary lighting - that will probably be the subject of a future post :)

Thanks again.


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PostPosted: Mar 15th, '18, 11:52 
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It will be interesting to see how your numbers look when you get this going.

I'm not sure it will make any difference in the temperature of the water but you could experiment with running your system as Constant Flood during the winter. Worth a try since this wouldn't draw cold air into the bed as there is no drain cycle. I think if you do a search someone already has looked at this although it might be easier if they just chime in.


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PostPosted: Mar 15th, '18, 21:08 
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Gabriola wrote:
how will the nitrifying bacteria react to being repeatedly exposed to cold air, then doused in relatively warmer water?


I personally don't think it will be any problem at all. Nitrifying bacteria are present everywhere, and I'm sure that their survival isn't something that you should be concerned about. I think there's a thread here about someone freezing media to save bacteria for later use.

The nitrifying bacteria will work and multuply at a much slower rate as you mentioned, but its ok because as scotty mentioned the metabolism of the fish also slow down, so the bacteria has less to do anyway, and finally any lag ie unconverted ammonia is less toxic in colder water anyway. Finally, related to an extent is that oxygen carrying capacity is increased with reduced water temps.

Bacteria should thrive as long as the system isn't really badly designed, and media is overloaded with solids etc. Plants will obviously grow as long as the conditions are within there tolerance levels. The fish are the tricky part, and if you choose cold-water species, which i assume you will, summer may well be more of a challenge than winter!

I think watercress is a hardcore herb which people grow through winter in AP in places pretty far north. Alternatively you could routinely remove and mineralise solids, topping up system with rainwater, and use mineralised solids in a separate indoor hydroponics system with lights and warm temps. Or if the greenhouse is good enough you could go the whole hog, supplement lighting and try to grow throughout the year!

I have to admit though I don't understand the need for MBBR. If the idea is to remove solids you would want radial flow, if it's bio-filtration you need, that is provided by GBs, if you want to minimise heat exchange you can easily adjust it to constant flow. A hybrid filter with radial flow collection at the bottom and floating media around standpipe at top could be very effective at removing solids, but MBBR with no prior removal of settling solids just seems counter-intuitive to me.


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PostPosted: Mar 16th, '18, 06:51 
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I'm finding it very encouraging that people are telling me that I shouldn't need the MBBR. Maybe I don't. My thought process for including it in my design went something like this:

-Are the nitrifying bacteria going to work in my grow bed during the winter?
-I don't know.
-What are my options if they don't?
-Well, an MBBR would do the trick and wouldn't cost too much.
-What are the downsides to an MBBR?
-None that I can think of.
-An MBBR would be kinda fun to build, and would impress my friends when I'm showing off my system.
-Right then, an MBBR it is!

Maybe not the most scientific reasoning, but it is what it is.
I'm also trying to avoid removing solids from the system, partly because they are valuable nutrients and partly because I don't want the hassle of a waste stream that requires additional handling and treatment. But I also recognize that I'm a newbie at this and I should heed the words of the experienced AP gardeners.

One detail that I haven't mentioned yet, is that once the system is up and running smoothly with rainbow trout I'd like to switch to salmon. Salmon need cool, clean water with lots of oxygen so I'm going to try to hit those targets even though the trout are a bit hardier.

I do want to run the system year round; having fresh veggies in the winter is a big part of the reason for doing this. It should be doable in our climate here on the coast.


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PostPosted: Mar 16th, '18, 12:10 
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scotty435 wrote:
I eventually hope to shift back to trout but don't plan on heating the water (might have to cool it a couple of times each summer though). Right at the moment I'm having fun growing catfish and bluegill


Scotty435, I'm curious as to why you changed from trout to catfish/bluegill. Were the trout difficult to raise?


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PostPosted: Mar 16th, '18, 15:07 
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Trout aren't that hard to grow if you have the right conditions. I switched from an indoor basement system where it was easy to control the temp, to an outdoor and greenhouse combination where temp was more difficult to control. Some years I could grow trout outdoors but other years the water gets too hot and they would not survive. When you have trout, getting a water temp close to 75 F can be lethal, no worries with bluegill and catfish so just makes things easier. Some system modifications or something like a chiller would probably get me through the hot spells but again would add to the cost. Having a larger amount of water and playing with when the water goes through the grow beds might work as well. Finally, using a DWC covered with styrofoam rafts might help keep the temp lower than using grow beds. Gordon (Gunagulla) uses a solar powered setup to run a chiller so if you're curious about that you might want to check out his thread.

I prefer the taste of trout but bluegill and catfish are pretty good as well.

FWIW - I haven't found catfish easy to grow with our cooler temps and lost a lot to disease. Bluegill have been pretty much bullet proof but grow relatively slow and don't have great feed conversion. The feed conversion doesn't bug me but I'd like to see them breed in system and have faster growth rates. They grow faster for people in warmer climates but still nothing like trout or tilapia.


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