Ok, I've been reading a ton, but for some reason my brain is having a difficult time wrapping my head around the fish / FT to GB ratio. I think I might have it, so for those in the know, does this sound about right?
I am planning to have a 4' x 28' x 12"deep (112sqft) grow bed growing everything from tomatoes to peppers to cukes/zucs.
So, I would need 112 fish, therefore a 784gal tank, right?
I would also have some worms in the bed. I would also be babysitting this thing like a newborn infant.
Jon Parr said:
Ask 10 different folks, get 10 different answers. Even the "experts" disagree, so no wonder you're having trouble with it. A commonly advised starting ratio is a MAX of 1 lb o fish, to 5 gal of FT, to 10 gallons of media.
Now in my opinion, FT size is less important, so long as your fish are comfortable, and different fish may have different needs. For instance, brooding tilapia will often get territorial with males proving dominance and females getting harassed. Crowding will minimize this behavior, are very light density will allow for alone time and refuge. So let your gut rule tank size, and you'll figure it out as you go.
More importantly is the 1 lb of fish to 10 gallons of growbed. And many will push that to 1 lb to 7.5 gal GB once your experienced and have a very seasoned and stable system. Coincidently, 7.5 gal is 1 cubic ft, so that makes some easy math for your 112 cubic ft GB, as a seasoned MAX you can hold 112 lbs of fish, and more or less a 5-600 gallon FT. Now, hoping to start eating fish at a lb each, then 112 fish it is. 1/2 lb bluegill equals 224 fish. 2 lb catfish equals 56 fish, and 4 lb carp equals 28 fish. You get the idea. Trout? Probably less, since oxygen becomes more critical.
Take care of your biofilter and the rest will follow.
Yep, the 'general consensus' and 'rules of thumb' is that your 112 sq.feet of 12" grow beds should support a MAXIMUM fish load of 112lbs. Now, you probably wont need anywhere near that number of fish to grow your plants...less than half that amount would probably still be more than enough. Opting for 7 gallons (or more) of fish tank per 1lb of fish (instead of 5-6) would give you a little leeway (O2, during power outages, more space for more fish in the future should you want/need etc...) Not necessary, but could be nice if you have the space/cash...
Now, are wanting to go 'au natural' and give your system about a year to build up a store of excess nutrients while growing only lettuce type light feeders in that first years time?
Most folks think tomatoes are heavy feeders (which they are), but cukes and zucchini have them beat by a long shot!
Cucumbers (and most cucurbits) are ABSOLUTE POTASSIUM HOGS which require a 1:1.2 ratio of nitogen (N) to potassium (K), and K is one of the plant essential elements that is as a rule, almost always lacking in a new AP system. Cycling with hummonia instead of ammonia can help this to an extent. But, if you don't want to wait the year or so for your system to 'mature' then...
Get yourself some potassium bicarbonate (KHCO3). Use it to buffer up your pH when the time comes, and use 4 teaspoons to a gallon as a K foliar feed (spray the leaves) and organic/fish safe preventative anti-fungal spray. (Many people will alternate between a calcium buffer like lime and potassium bicarbonate).
And you will want Epsom salt too. Cukes also need about a 1:1 ratio of magnesium (Mg) to calcium (Ca). Calcium if you have hard water is hardly ever a problem (more likely to have an excess than a deficiency, too much of it will mess with your plants ability to uptake both Mg and K). Epsom salt will provide you with some needed Mg and is fish safe.
Also until you get a handle on your pH some form of chelated iron, (or MaxiCrop + Iron) would surely be helpful once your leaves start yellowing between their veins.
Sorry for dumping all this on you at once, but if you want to grow those type of plants in your system right away, your gonna need this stuff...
Yep the guys are right.
But, what sort of grow bed/system will it be? If you are doing a simple flood and drain media bed system with no sump tank, you need to have enough fish tank volume to flood that bed and drain it without stressing the fish out too much. So at the low water level, you still should have at least 5 gallons of water per fish in the tank
But anyway, for stocking with small fish that only grow out to a pound. One fish per cubic foot of grow bed media is a good starting place and then you harvest as they get up close to a pound.
As noted, some fish get bigger and so you should stock less of them. My big system had 1400 gallons of grow bed media and 700 gallons of fish tank (plus sump to handle water level fluctuation) and I would stock 70 channel catfish in that for grow out.
Having twice as much grow bed as fish tank (provided you can accommodate the water level fluctuation some how,) lets you stock your fish tank quite heavily once you are at the point that you no longer need to ask some one else how many fish. Now I don't want to hear anyone telling newbies the MAX stocking rates since if they have to ask how much fish they can stock, they are not ready to handle the max. Having a cubic foot of grow bed per fish (planed grow out of up to 1 lb each) is a reasonable rule of thumb. Or the way they recommend in oz, 20-25 fish (500 gram planned grow out) per 500 liter grow bed.
Thanks a lot everyone.
My biggest concern is that I have enough fish to support the plants. It sounds like I should start off with about 60 fish. I definitely don't want to start with the max, I think I was reading the max numbers to be what I needed.
The system is a flood and drain. I was thinking of somehow using 2 tote size containers, and dig a sump under the bed. I was originally thinking of digging the tank under the bed, but I couldn't get one big enough to support the drain from the system.
I appreciate the help!
Plan on at least a 400 gallon sump. 4'x128'x1' = a volume of 837.82 gallons (depending on the size/density of your media blablabla-blabla figure 38% displacement. You wont be filling the bed to the brim with media anyways AND you'll only be filling it within 2" of the top of the media and all that, but figure on a 400 gallon sump anyways.
Jon, gotcha. I'm thinking of harvesting around the 1lb mark so that would be about 60 lbs of fish.
Vlad- wow a 400gal.. I was thinking around 168, but that number was a 40% of the fish tank, not the grow bed. Makes sense.
Yep, and then there's that. Which is exactly what I did... 8 IBC grow beds ranging from 14" to 18" deep, a repeat cycle timer and a low flow sequencing valve, filling 4 sets of 2 in sequence.
If you're not dead set on one big 'ol 28' long grow bed it might be something to think about. BUT (yeah, there's always a but)... since I remember that you too live where it gets real damn cold for long, you still might want a big fat sump so that you can switch to constant flood in the winter time. Since in a flood and drain scenario, when the air temps are real cold and you are heating your water, the media will act as a cold sink, the 'warm' water you heated will flood a bed full of air cold rocks and cool down right away. not so with constant flood. Then if the power goes out, and your back-up system should fail, all that water (in a constant flood) still needs someplace to go...So I still have a sump that can handle all 8 beds draining at once. I tend to plan for stuff like that, because stuff like that seems to happen to me. I must've been even more of a prick in a previous lifetime or somethin'...
Jon Parr said:
If you can divide the growbed and rotate floods with a sequencing valve, then you can get by with a smaller sump, or use the FT as sump
Yeah, huge beds (from what I've gathered) seem to come with their own set of specific 'problems', luckily there are usually solutions to apply. IMO 6 feet is plenty long. 4 or 5 - 6' long by 4' wide beds with a sequencing valve on a timed flood and drain (no siphons is music to my ears :) might be good IMO.