Backyard Aquaponics
A place to discuss aquaponics

Small fish still put out plenty of ammonia.

I would personally recommend cycling up fishlessly so you have a good bio-filter and plenty of nutrients available to get started at least with greens before you even get fish. And then small fish you can often start of on somewhat higher protein feed which will produce plenty of ammonia early on.

I never recommend Over stocking early expecting that some will die because what usually happens is your bio-filter isn't prepared to handle the heavy load early on and you can easily have such bad water quality (ammonia spikes) that you wind up killing ALL the fish instead of just reducing the numbers down to what you should grow out.

As Ron Says, little fish produce plenty, and during your first season (even if you cycle up fishless) your bio-filter will still be immature and you don't want to push things.



Lots of research is a good thing, so long as you still manage to get started. Try to make your structure one where you can open up or remove as much of the covering as possible for summer but still easy enough to close back in for winter. I did a cattle panel greenhouse where the arched panels were actually mounted up on posts so the sides were all open and I could roll them up in the summer. If you can also figure out how to manage a center top ridge vent you will be able to take advantage of cooling by convection as well simply by opening a small vent along the bottom sides.

@ronmaggi I had no idea that small fish could provide enough ammonia. The place that I found in Missouri has 3 sizes of catfish: 4-6 inches, 6-8 inches and 10-12 inches (10-14 cm, 14-20 cm and 25-35 cm - I did this in my head so if my conversions are not right, sorry. I do like metric even though I live in the US). Would you get a mixture or all one size?

@ TC Lynx I have read on the forum of cycling up fishlessly, but don’t know enough about it. Back to perusing the forums! I had casually wondered if that might be a good thing to consider. So, I am pleased to know that it is. Having the bio-filter up and running and nutrients available to plants sounds really attractive. I just need to figure out how to do it. One of my biggest concerns was how was I going to get all this started. I had considered buying an aquarium etc., but this seems like it could solve the problem more efficiently.

Our plans for the greenhouse include a 1 foot board at the bottom below the end of the cattle panels. I can easily envision making a hinged section that we could open as needed. We were going to put vents in the ends of the greenhouse that could be opened and closed. But your idea of a ridge vent is an excellent one and more research is in my immediate future.

JL

Right now I've got a dozen 4-5 inch cats in my little greenhouse. Hard to say if they are providing enough ammonia as it always tests down very low so the plants are using it. I guess the plants are getting enough, they are doing pretty well although these below freezing temps takes the greenhouse down into the mid to upper 60's at night and I understand those temps retard growth a bit

Here is a blog post I did on fishless cycling
http://www.aquaponiclynx.com/fishless-cycling

And if you search here, I know some of my early system threads and the pee ponics thread probably have some useful info. And then I'm sure that somewhere in the Useful info section or the Basic Info Section you will find some threads on cycling and fishless cycling.

I have not raised catfish, so I don't know how aggressive they are to each other. TCLynx might be better to answer that question. One size of catfish, or mixed sizes?

I am getting a bit closer to having a basic understanding of some of the major concepts.

I have a question about the 2:1 GB/FT ratio. How do you calculate the volume of the GB?
If I have a GB that has an empty volume of 1000 liters:

Assume that I fill it with media that takes up 62.5% of the volume and that I leave 5 cm open at the top and keep the water level 5 cm below that.
a) do I use the volume of the empty GB
b) do I use the volume of the growth media (since the plants will be growing above the water level)?
c) do I use the volume of the growth media that will be covered by water?
d) do I use the volume of water that will be in the growth media?

I do plan on using rectangular beds, but wonder how you would calculate in a half barrel? (I can do the math if I know which of the alternatives are correct.)

I have seen some systems that have a combination of growth beds and NFT. How does the presence of NFT factor in to the 2:1 growth bed ratio? (I will hold off any more NFT questions until after I peruse the forums some more)

Thanks again for all the information you all are providing.

JL

By the way the peeponics is quite interesting. I guess there will be a couple of jugs I need to fill pretty soon.

Fill those jugs sooner than later, it is best to let it age. There are some forum members that will give a more precise answer on the growbed media info, but I just consider the volume the media takes up. I.e. A half barrel's worth would be about 26 gallons. Don't worry about the air ( or water) space.

I'd only count the media that gets damp as part of the filtration. However many pebbles it takes to fill a 1 gallon jug is 1 gallon of media (air/water spaces and all - basically what Ron said on this). I wouldn't worry too much about this though because the 2 to 1 ratio isn't etched in stone.

Guys keep it simple.
If you have say a 100 gallon fish tank and you want a 2:1 Grow bed:fish tank ratio, it is the overall volume of the containers.
So if you cut two 55 gallon barrels in half (to make 4 25 gallon grow beds) you have 100 gallons worth of grow bed and 100 gallons worth of fish tank which would be a 1:1 ratio. You would need a total of 200 gallons worth of grow bed (total container volume assuming you fill it right up with media) to get a 2:1 ratio of grow bed to fish tank with a 100 gallon fish tank.

If you go building 1' deep rectangular tanks you can the go and use an online calculator that can convert cubic feet or inches into gallons or vice versa to figure out from cubic measure to volume.

Now if you want to know how much the water will fluctuate in a sump tank when you have some amount of media beds, well about 40% of the total volume of the grow beds is about how much water is needed to flood the beds. This is just a wild estimate since it of course varies based on the exact size of media and how deep you flood but 40% is a good average. So I generally recommend sump tank sizes need to be at least 50% of the total volume needed to flood the grow beds and I will often recommend adding a bit more to the sump tank size since most pumps can't suck a tank totally dry and you want to have a little space left for evaporation or installing a float valve and stuff like that.

Yes, bottle up some of that pee ASAP to let it age since if you use fresh pee, the urea isn't converted to ammonia yet and won't be easily measurable. Also sealing up the pee to age for 3 weeks or more can have the effect of elevating the pH and letting the ammonia kill off pathogens like e. coli which exists in and on all of us warm blooded creatures.

OK, here are some tentative calculations.

Right now we are planning on 2 growth beds each measuring 4x8x1 feet. Filling to 10 inches with creek rock (probably) and filling each bed to about 8 inches with water from fish tank.
4x8x1= 32 cu ft
filled to 10 inches = 26.67 cubic feet, 200 gallons, 755 Liters
Water to 8 inches (42% of volume)= 9 cubic feet (67 gallons, 255 Liters of fluid in each bed)

X 2 beds = 53 cubic feet, 400 gallons, 1510 liters media volume
= 18 cubic feet, 134 gallons, 510 liters fluid

Fish Tank:
8x4x3 feet = 96 cubic feet, 718 gallons, 2718 liters
Filled to 2’3” = 72 cubic feet, 538 gallons, 2018 liters

For fish calculations:
Need about 30 kg fish (2kg/100l) or 53 (1lb/cu ft) so can take 55-66 pounds of catfish at mature weight.

For pump calculations: Need to pump 2000 liters/hour

We thought we'd make the fish tank larger than needed for 2 reasons. There should not more than about a 25% fluctuation in the fish tank even if we went to intermittent pump and drain and we wanted to put in extra space for the possibility of future expansion.

So, are we way off track or does this sound reasonable?

Thanks

JL

I will recommend that when you fill the beds, FILL them right up to the rim. Even gravel settles with a little time.
Make sure you keep the stand pipes accessible (removable) so you can adjust the flood height and stuff.
There is no getting a drill down into a gravel guard to adjust the size of the holes in a stand pipe if decide it needs to change.

Make sure you look for pumps with a curve or chart that will tell you how much water it moves at different heights since your minimum of 2000 lph needs to be moved at whatever height above the low water level of the fish tank or sump tank that the pump has to lift to. Make sure the pump is at least a little oversize especially if you are planning to expand. Install a bypass with a valve to adjust and spray excess flow back into the tank with the pump which will provide extra aeration without choking back the pump in case you have too much flow to send all of it to the grow beds or where ever.

Once fishlessly cycled up I would recommend starting with perhaps 25-30 channel catfish for your first season with fish.

I would recommend sticking with one type/size fish since my experience with trying to stock channel catfish with different species is that if you want to say catch the bluegill or faster species, you tend to beat up your slower big channel catfish in the process. I now prefer to have a separate tank per species/batch of fish so I'm not messing with accidentally catching the wrong ones when we go to harvest. Catfish have sensitive skin (no scales) so are prone to net injury and tend to be scardy cats so handling and nets swinging around in their tanks tends to be very stressful to them and between that an injury risk, I like to minimize handling of them as much as possible.
We never net our fish for "show" If we net a fish, it generally needs to get harvested. I found that if we go swinging around with a net on more than one day within a week, I'm likely to have injured fish that could die several days later. So if we do a large harvest one day, I'm normally not willing to do another harvest during the next several days.

The Channel Catfish is usually not eat the evening after they have been scard by the net in their tank. Small fingerlings are an exception, they sometimes are so hungry they will eat even the evening after being transported but don't push it. Over feeding always kills more fish than under feeding ever could.

What rate os seasol and how frequently can it be added?

With Seasol or Maxicrop original (the kinds with no added fish fertilizer and therefore low nitrogen levels) you can actually be pretty flexible on how much you add.

Take note, if you add too much your water will be dark brown and you won't be able to see your fish. If you don't add much you won't have much potassium or trace elements for your plants.

I have in the past recommended that people base the amount they add on the square footage of their grow beds. For instance if the bottle says to water 100 square feet using 1 oz of concentrate mixed into a gallon of water and you have 100 square feet of grow bed then you would use 1 oz of concentrate poured into your grow beds.

When your system is new you might want to use a bit more and perhaps use it more often but as your system matures you may not need as much, by then hopefully you will be able to look at your plants and see when they are wanting something.

I have used about 4 oz for my system (I use Rootmagic), plant growth has been good, but like TC said, it does make the water too dark to see the fish below about 6" depth. I do weekly water testing and look for floaters...so far none. Coming up on 7 months and all good.