Tilapia in Isolated Stock Tank

[Ryan Rogers]

Sylvia - thanks for the invite to the group and for pointing me to the Gator Farm for tilapia fingerlings. I've emailed them and am waiting for their response.

 

I wanted run my plan for tilapia by everyone and see if anyone had any suggestions. I recently built a 12x16 greenhouse up at 7600 feet in Evergreen, CO, in which I will grow vegetables in soil (seeds
started sprouting today!) . In this greenhouse I have placed a 100 gallon black
stock tank that I picked up at a garage sale for $10. The main reason I put it
in the greenhouse was for thermal mass, but also want to experiment with growing
out fingerling tilapia for the table/freezer. Obviously I'll need to heat it,
but that's okay because the heat will just escape into the greenhouse which will
need it anyways. For aeration I planned on just doing an air pump with airstone.
I'll probably feed commercial (Aquamax?), with the occasional vegetable scrap
tossed in. Maybe I'll grow some duckweed on the side as well...

 

My main question is about filtration - since this is a "closed tank" and not tied into a hydroponic system (not yet!), my plan was to drain water out the bottom spigot daily, individually fertilizing my plants
in the greenhouse. Will this approach be enough to keep the water quality good
enough for the tilapia, or do I need an actual filtration system? If it would
work, how much should I drain off on a daily basis (10%? 25%?).

 

Is there anything else I would need to do to "treat" the water for tilapia? I'm on a well, which was recently tested and is good water (for people at least)...

 

Finally, in terms of density, if I followed the 1/4 lb fish per gallon rule, and planned to grow them out to 1 lb (that is normal harvest weight, right?), then I should probably only put in 25 fingerlings,
correct? Any way I can up that density without jeopardizing the
fish?

 

Anything else I'm forgetting?

 

Thanks for everyone's input!

[Jeff Givan]

Welcome Ryan!
Personally I would add a bio filter to the tank, which would be really easy. Basically you could have 5 gallon bucket suspended over the stock tank. Pump water up to the bucket and let it flow over some kind of media. There is a wide range of stuff you can use. I use a lot of those plastic pot scrubbers, you can also buy specialized products online for this. You want to slowly add the fish because you have to start the biofilter slowly. Sylvia has a great blog added to this website up at the top. In there is a great article on the Nitrification process that you should really read before adding your fish! Sure hate to kill some good fish!

[Ryan Rogers]

Thanks Jeff! Hmmm... I might have to get creative with some tubing to/from the tank to the biofilter bucket, as I have already built a flip down workbench directly over the stock tank.

So, from what you have told me, and what I read from the Nitrification article by Sylvia, let me see if I got this: hang a 5-gallon bucket filled with plastic pot scrubbers, continuously pump water from tank to top of bucket, and return filtered water to tank. Buy some "sacrificial" goldfish, and let them live (if they make it) in the tank for 2 to 4 weeks, or until ammonia levels drop to near zero, before adding tilapia fingerlings.

Does that work? Or have I left something out?

Question: with a biofilter in place, does that mean all my fish waste/plant nutrients get trapped in the filter? I'm still hoping to fertilize individual plants with warm water from the tank (replenishing the tank with fresh water accordingly)... or will the tank water still be nutrient rich?


Jeff Givan said:

Welcome Ryan!
Personally I would add a bio filter to the tank, which would be really easy. Basically you could have 5 gallon bucket suspended over the stock tank. Pump water up to the bucket and let it flow over some kind of media. There is a wide range of stuff you can use. I use a lot of those plastic pot scrubbers, you can also buy specialized products online for this. You want to slowly add the fish because you have to start the biofilter slowly. Sylvia has a great blog added to this website up at the top. In there is a great article on the Nitrification process that you should really read before adding your fish! Sure hate to kill some good fish!

[Shawn]

You could easily just put a bulkhead fitting with the appropriate size tubing and run that into the tank and around your bench. I also think there should be plenty of good nutrients left over in the tank, as a bucket is only a small amount of what is usually deemed appropriate for a media to tank ratio ( often 1-1 or 1-2 gallons to media, depending on amount of fish).

Ryan Rogers said:

Thanks Jeff! Hmmm... I might have to get creative with some tubing to/from the tank to the biofilter bucket, as I have already built a flip down workbench directly over the stock tank.

So, from what you have told me, and what I read from the Nitrification article by Sylvia, let me see if I got this: hang a 5-gallon bucket filled with plastic pot scrubbers, continuously pump water from tank to top of bucket, and return filtered water to tank. Buy some "sacrificial" goldfish, and let them live (if they make it) in the tank for 2 to 4 weeks, or until ammonia levels drop to near zero, before adding tilapia fingerlings.

Does that work? Or have I left something out?

Question: with a biofilter in place, does that mean all my fish waste/plant nutrients get trapped in the filter? I'm still hoping to fertilize individual plants with warm water from the tank (replenishing the tank with fresh water accordingly)... or will the tank water still be nutrient rich?


Jeff Givan said:

Welcome Ryan!
Personally I would add a bio filter to the tank, which would be really easy. Basically you could have 5 gallon bucket suspended over the stock tank. Pump water up to the bucket and let it flow over some kind of media. There is a wide range of stuff you can use. I use a lot of those plastic pot scrubbers, you can also buy specialized products online for this. You want to slowly add the fish because you have to start the biofilter slowly. Sylvia has a great blog added to this website up at the top. In there is a great article on the Nitrification process that you should really read before adding your fish! Sure hate to kill some good fish!

[Jeff Givan]

The biofilter will change the ammonia to the nitrites that the plants need. It won't take away nutrients it will help create them. The only thing you might loose is some of the solids which really aren't that big of a deal, and you could re-capture those if you really wanted too. Shawn made a good suggestion on the bulkhead fitting, you could also drill a couple of holes in the back of the work bench to run the tubes through. They would only be a 1/2" or so. There is also a supplier of White Tilapia in Kansas City if I remember correctly and you can also get Blue Tilapia from the link in the Tilapia Group thread. There is a lot to learn with all of this and your in the right place to learn it. There are some really great folks here and I have learned a ton already!

[TCLynx]

You definitely need some sort of filtration! Ammonia can build up to deadly levels if you are trying to feed up the tilapia to get them to an edible size.

The bio-filter will convert ammonia to nitrite and nitrite to nitrate which is what the plants want anyway but since you don't have any planting area for your fish tank, you will definitely need to be pulling out nutrient rich water daily and topping up with fresh to keep the Nitrates down to a reasonable level. There will definitely still be good stuff in the water for the plants.

As to numbers of fish and cycling up. Tilapia jump so if you fill that tank to the rim for the full 100 gallons, you will likely loose fish over the edge. I recommend netting over the tank to keep the fish from jumping out under the edge of your work bench. Some rope or a bungie could hold some screen or netting and still be easy to pull out of the way for feeding and such.
But about the 100 gallons. I don't think that entire 100 gallons will be completely usable as fish space so you might want to keep that in mind for your fish to gallons calculations.

There is a method of fishless cycling that might be of interest to you if sacrificial goldfish are not your style (or if they cost more than you expect.) You can cycle an aquarium or other bio-filter using an alternative ammonia source. I recommend you get a freshwater master test kit before you start cycling and definitely before you get any fish. Anyway, you can dose your fish tank up to 1-2 ppm of ammonia and then let it run through the bio-filter until the ammonia goes down and nitrite goes up. Eventually the Nitrate goes up and you can dose again. When you reach a stage where you can dose to 1 ppm of ammonia and within 24 hours the ammonia and nitrite are both back to 0, then you are fishlessly cycled. My personal favorite alternative ammonia source is Hummonia or Pee. I usually seal it in a bottle for a couple weeks to let the urea content convert into ammonia, this makes dosing without overdosing easier and also has the added benefit of killing off things like e. coli that are normally present on our skin and can easily get into urine. If you think pee is too yucky to cycle your fish tank, then you can get some urea fertilizer. Beware with urea fertilizer, it doesn't show up as ammonia immediately, it has to wait around for naturally occurring enzymes to show up and convert the urea to ammonia, this can take a while and it is easy to overdose a system to a little bit and be patient. Pure ammonia if it can be found can work too but finding pure ammonia can be difficult as most cleaning products have fragrance or detergent added which would be bad for a fish system.

Good Luck.

[Ryan Rogers]

Thanks everyone! I now understand much better the role that the bacteria plays in the system.. and thanks, TCLynx, for the tip on the netting..

So it sounds like there are 3 main pieces of equipment I need to purchase: heaters (600W total I think), an air pump with airstone, and a water pump (submersible?) to push water via tubing up to my biofilter. Any specific recommendations that would be appropriate for my size tank? I'd like to go more on the cheap side since this whole thing is a side greenhouse experiment...

Thanks again to everyone...

[Jeff Givan]

Well there are many ways to heat the water without an actual heater, there is always solar to start with. You can also use a compost pile with tubing running through it. See this link at youtube to get the concept.
http://www.youtube.com/watch?v=ILzxOH6n7-c
You just have to become Mr. Wizard Ryan :)

Ryan Rogers said:

Thanks everyone! I now understand much better the role that the bacteria plays in the system.. and thanks, TCLynx, for the tip on the netting..

So it sounds like there are 3 main pieces of equipment I need to purchase: heaters (600W total I think), an air pump with airstone, and a water pump (submersible?) to push water via tubing up to my biofilter. Any specific recommendations that would be appropriate for my size tank? I'd like to go more on the cheap side since this whole thing is a side greenhouse experiment...

Thanks again to everyone...

[TCLynx]

Air, You want an air pump that can deliver at least .25 CFM at 2 psi and an air stone and appropriate size tubing for that .25 CFM.

Water pump, well you need to move your 100 gallons each hour but I think a 100 gallon per hour pump would turn out to be too small for you. Something between 250 and 500 gallons per hour at a couple feet of head will probably be appropriate (and you can probably get it for around $30 or less and it will probably not use too much electricity either.) Remove any sort of sponge filter and you might want to put it on a timer to shut off for a few minutes each day to hopefully dislodge anything that will tend to block it up and slow it down regularly. You will still probably need to check it regularly to make sure it's still flowing properly.

I won't make any comments on heaters as I have not much experience there. I've quit growing many tilapia anymore cause I couldn't keep their water warm enough over winter and I wasn't willing to buy heaters. I have catfish now and they are great.

[Ryan Rogers]

Jeff - thanks for the link to the compost water heater - pretty cool. I think for now I will go ahead and use some traditional electric heaters. I am already using electric to heat the entire greenhouse, and so heating the water shouldn't add too much, especially since the escaping heat will just go right into the greenhouse, ultimately cutting down on how much those heaters have to run.

TCLynx - thanks for the specs on the pumps - definitely puts me on the right track. And if I was planning on wintering my system, I'd definitely look into catfish, but since I'm planning on shutting down the greenhouse Nov - Feb, I need the fast growing tilapia.

One more question: how do I control the amount of water going into the biofilter, to make sure that its not faster than it can drain out? Just a simple valve before the bulkhead fitting going into the bucket? That won't put stress on the pump will it?

[TCLynx]

to control the amount of water going into the bucket (and do put big enough drains on the bucket so that you can get at least 100 gallons per hour going through the bucket if not more) simply run pipe out of the pump then above the fish tank water level put a T one feed will go to the bucket, the other feed will get a valve and run water back into the fish tank. The amount you open the valve, the more water bypasses the bio-filter and goes directly back to the fish tank. You can adjust how much water the bucket gets by adjusting the bypass valve.

On the bio-filter bucket, it is best if you have the water go into the bottom of the bucket and flow up through some media and then flow out nearer the top and then go back to the fish tank.

[Ryan Rogers]

Interesting - so the pump should push the water up through the media as opposed to gravity pulling it through. Just curious - why?

Thanks for the bypass explanation - pretty slick...

[TCLynx]

If you were to say have the water flow into the top of a bucket of media and have the drain in the bottom. With a very small container like a 5 gallon bucket in relation to a 100 gallon fish tank. Well You run dirty fish poopy water into the top of the bucket of filter media or even gravel, that media is going to clog up with bio-slime and fish poo and then the bucket is gonna overflow out the top rather than letting the water flow quickly enough down to the bottom and out the drain. To be able to flow in at the top and drain out the bottom, you need a larger amount of gravel than you have fish tank.

Think of it kinda like a waterfall filter like they use for ornamental ponds. Where the pump is in a skimmer box or down in the pond and pumps water up to the bottom of the waterfall bin and then there is some filter material and lava rock or whatever and then the water flows out the waterfall spillway.

But if you run the pipe from the pump down to the bottom of the bucket and put a few extra pipe fittings like T's on it to disperse the flow a little and then put the gravel on top and have it flow up through the media, it will keep flowing far better and be far less likely to overflow all over the floor and run your fish tank dry.