New Raft System

[William Mancuso]

Just finished building my DWC system.  First the sytem specs.  Their is a 1000 gal fish tank, two 16' x 4' raft beds and an 8' x 4' fload and drain germniation bed that flows back in to the fish tank.  The system was filled with well water ph of 7.0. I did a system start up will about 20 fish 1" - 6" in legth.  Total wieght no more than 5 LB. I will be going to get 1200 1" bluegill to put in the system, about 75 LBS. For the past week water temp has been 65 - 70 and  have had no measureable nitrite, nitrate, or ammonia. There are rosy red minnows in both grow beds as well as some ghost shrimp.I've been using a multi strip to test, and a seperate ammonia strip. Both grow beds have two air stones as does the fish tank.  The fish seem to be perfectly happy.  Sence day one I've had shade over my tank and the rafts in the beds. Out of the 156 seeds I've planted 100 have sprounted in 6 days.  The seed that have not sprounted might take a bit longer as they are different plants.  All togeather I've got a 90%-95% germination rate.  Will be moving starters in to raft beds in about a week.  My worry is that I've got no measureable nutrient in the system, at levels good or bad.  Total grow bed area 128 sqft, total systen water about 2000 gal, and am in the panhandle of Florida.  I will be growing most all veg this year to see what can be grown and what can't.  Some folks tell me I can't grow veg like tomatoes, and squash in a raft system. Then some folks say you can.  I've becided to see for myself.  My main goal is to feed my family of five and sell the extra to the market. I've no experiance in these matters and would appreciate any and all feed back.

[Ron Thompson]

It's the 1200 fish that is making us all take a collective breath...  I'm not sure any but the largest commercial operations run that type of number. As fingerlings they won't be a problem but as they grow you will need to make changes. Start planning for a backup power source since the panhandle seems to get at least one hurricane every year. You will need a method to run the air pumps at least if you lose power. That number of fish would wipe out the air in just a few hours. I lost my fish in about 10 hours (overnight) when a fuse popped - I had 30 mature fish in a 650 gallons. That is 1 fish per 2 gallons, you have 1.2 fish per gallon (if water isn't pumping, the raft water won't help the air situation), so you have 4-5 hours of air at best.

I've never heard of tomatoes in a raft system, but no reason not to try. The bush variety would likely be the best bet. Though with the amount of nutrients you will have, I put a grow bed in too for the stuff that needs better root support (like tomatoes and peppers).

Quite honestly - my biggest suggestion is slow down. Cut back on fish for a season until you get a working understanding of what you are doing. Patience pays off.

[TCLynx]

The heaviest I ever stocked bluegill (for more than a few weeks of quarantine) was about one fish per 2-3 gallons of fish tank and I have twice as much media filled grow bed for filtration on that system.  And that was in my view a very heavily stocked system.

And my big system with the catfish I usually stock about one fish per 10 gallons of fish tank and I'll have twice as much grow bed as fish tank there too.

If you don't already have the bluegill, get way less!!!!!!!  Even 400 would be large number for a new system with extra filtration and solids removal.

I also recommend getting the Freshwater master test kit.  The test strips are not very reliable.

Tomatoes can grow in a raft, you just have to support them from above.

However, I see no mention of additional filtration for that system.  With heavy stocking and simply flowing poopy fish water directly to a raft plant bed with no solids removal or filtration before it, I fear the fish poop will just coat your plant roots and make them struggle to get enough dissolved oxygen and the plants will struggle.  You may find yourself with a stinky mess.  The Friendlies micro system design that doesn't use any filtration generally relies on very low fish numbers to keep from sliming the plants.  Like maybe 1 fish (that might grow out to 1 lb) per three square feet of raft.  Which means to me if you will harvest your bluegill at 1/3rd of a lb then you might stock one fish per square foot of raft.  Since you already have goldfish and koi in there, I would only add about 100 bluegill.

[Ron Thompson]

Ron Thompson said:

- I had 30 mature fish in a 650 gallons. That is 1 fish per 2 gallons, .........

 

math goof -- I meant I had one fish for every 20 gallons. Using that ratio, your system may only have a single hour of reserve air if the power goes out and your stocked at the levels you propose. That leaves you not at risk of a power outage but an algae bloom could be all it takes to kill off your fish.

Listen to TCLynx - she knows her stuff and won't steer you bad.

[William Mancuso]

What is more important fish wieght or number.  Right now I've only about a pound of fish per 200 gall of water.  I return with 1000 bluegill total wieght 4 lbs.  total fish wieght around 10 lbs.   I was under the impression i needed 40 -60 lbs of fish for my system.  I will thin the fish out at 6 oz to get the wieght right .  Or am I looking at the wrong things here?  I know the fish will get bigger and I can fix that when the time comes,but what is the the wieght of fish yall have in your system?  does one fish per 10 gallons of water work if the fish are tinny?  I'm not wanting to be argumentative here just trying to understand. When you say one fish per 10 gallons of water is that one 5 lb fish?

[TCLynx]

William, you have never answered the question about "do you have any additional filtration?  do you have solids removal?"

If you have extra filtration and solids removal, I think perhaps your system could then handle 60 lb of fish but you would need boko air and backup to make sure the fish were not going to die.

If you don't have solids removal and additional filtration.  Then 40 lb would be the max amount of fish the system could support.

Just because a system can support 40-60 lb of fish.  THAT DOES NOT MEAN YOU NEED THAT MANY FISH IN ORDER FOR THE SYSTEM TO WORK.

In commercial operations they will go to great efforts to keep the fish load as steady as possible (this often means multiple fish tanks so they can stagger stocking and harvest to keep a steady supply of nutrients.)  However, if you are planning a backyard system then those lengths are not normally necessary.

I would say get between 100-200 bluegill for that system.

The ratio is not how many lb of fish per volume of water.  The ratio is to balance the amount of fish with the amount of filtration you have to support them and then hopefully balance that with the right amount of plants so they use up the nutrients but are not starving for nutrients.

Don't plant all your super greedy plants right away, a new (not yet mature) system is usually not complex enough yet with nutrients for all the fruiting plants during the first part of cycle up.

When I re-stock my big system.  I will usually harvest out the last few big guys (talking the 5+ lb channel catfish) and by then there have only been a dwindling number of big fish left in the 700 gallon tank for a while.  Then I will re stock with under 100 small fish.  Actually usually just about 70 of the 6-8 inch fingerlings which will take about 8 months for most of them to get up over 1 lb.  At which time we will start harvesting some so by the time we are talking about 3+ pound catfish it's been a year and there will probably only be half of them left in the tank and when we are getting the 5+ lb fish we are usually getting ready to get new fingerlings into quarantine so by the time we harvest all the big fish out we will have fingerlings ready to go in.

It is also common to feed small fingerlings a higher protein feed so you don't necessarily want a MAX  load of fingerlings since their waste will be more potent from the high protein feed and the fact that small fish will eat a higher % of their body weight per day as well.

So I can't tell you exactly how big the fish are when I put them in but normally if they recommend say 40 lb of fish (for the amount of filtration and plants), I'll simply stock 40 small fish and let them grow out to as much as a lb each.  Now with bluegill that you are likely to be eating at 1/3rd of a lb, and if your filtration system can support up to 40lb of fish, then I might say you can stock up to 120 bluegill so that as they grow out to that 6 oz size you will then be able to start harvesting and letting some of them get bigger but still not be going grossly over your 40 lb load.

[William Mancuso]

I have no extra filtertion or solid removal in place. But at your recomendation I can go to the drawing board and add a bio filter in a 30 gal bin from the fish tank and consider a small gravel bed before the germination bed.  Although my funds are spent.  I will have to jerry rig something temporary for now.  I've got a small gas jenny for power interuptions.

[William Mancuso]

I just bought a maaster test kit from petsmart and thought i would post the levels in my system. ph is at 7.6 ammonia .5 nitrite .25 and nitrate is at 5.0  my ph seems to be high any suggestions on how to lower it?

 

[TCLynx]

Patience, 7.6 is a fine pH for a new system.  Aquaponics has a naturally acidifying effect and over time that pH will likely drop and you will probably have to add some potassium bicarbonate alternating with either hard water or some calcium carbonate to keep it from dropping too far.  Keep an eye on the pH so that you can take action before it drops much below 6.5 since if it drops too low too fast, you could upset or even crash your bacteria and see major ammonia spikes.

At a pH of 7.6 you might see some iron lock out and need to dose with chelated iron but it isn't an outrageously high pH and I've run systems for years at a pH of 7.6. 

Ideal would be more like 6.8 but lowering your pH is generally not a good idea in a system that already has any fish, plants or bacteria in it since you are likely to go too far or cause pH bouncing by adding acid.  If there is something in your system that is keeping the pH high, adding acid will only cause major pH bouncing and won't be good.  If you must use acid to adjust pH of anything, I recommend you get a separate tank or barrel to pre adjust your top up water and let it stabilize before you use it in your system