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Hey all!

    I have questions in regard to blue tilapia feeding and behaviors. I am a graduate student conducting thesis research with aquaponics. I transported 50 blue tilapia @ 450g  across state to campus, and they currently are dispersed among 5 1000L recirculating systems. I have lost 12 fish in the past 2 weeks due to fish aggression and a couple were due to nitrite levels. 

    The water quality is good now, D.O. 7.3, Ammonia and Nitrite 0-.5. Temp is 72 degrees F. Lights are currently running at all times. The tanks are blue polys. 

    Fish came from a greenhouse where they were raised with Niles in a large pool with a lot of algae/veg. growth within. The fish were fed an Aquamax floating feed.

   My fish have not eaten for the past week or so. I have tried numerous feeds, 32% floating catfish feed, carnivore floating feed (trout), wheat-germ floating feed, and sinking pellets for fingerlings. I have also tried crushing each feed type and they still will not eat it (pellet sizes varied among all feeds as well).  I have NOT tried an Aquamax floating feed (will take 3 weeks for the order to get in). I have also tried blending leafy greens. 

   I have read a lot of literature on these species and unfortunately the authors contradict each other (there is even a paper on the contradicting info). Some say they are omnivores, herbivores, filter feeders and particulate feeders, detritivors, opportunistic feeders, and pelagic feeders. 

   I am in the process of sexing the fish and will try to put 1 male/tank with females (suggestion of an aquaponic enthusiast). 

   Does anyone have any thoughts or suggestions for these problems? Should I buy the Aquamax feed? (My thoughts are if they will not feed upon other floating feeds they won't touch the Aquamax; or is there that much difference between the feed content as well as fish preference?). Next, is there any suggestions to alleviate the fish aggression? (they are constantly picking on each other)

Thanks!!!!!

 

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The aggression could be two things. First maybe they're wanting to breed or secondly the aggression may come from not eating.

Did you just get them or have you had them or have you had them awhile?

I have had them for about 3 weeks now. They will not eat anything. I actually just bought the Aquamax feed today and they would not touch it. I am thinking the aggression is coming from both hunger and breeding behaviors. I am starting to think that they fed upon the algae/veg. within the supplier's tanks instead of regularly feeding upon the pellets. I called the supplier he said he never noticed a difference between the nile and blue feedings though...

Tommy D said:

The aggression could be two things. First maybe they're wanting to breed or secondly the aggression may come from not eating.

Did you just get them or have you had them or have you had them awhile?

One thing is that your stocking density is really low.  When tilipia go into reproductive mode they stop/slow eating.  So coupled together all this new found room to claim as their own space and your going to have non eating and fighting fish.

I am also not sure that the nitrite might not have them feeding. 

I traveled across state with mine too, and they ate the same day.

What to do is based on the project at hand.  What are you going to try and accomplish? 

If they don't want to eat, don't push it.  They can go awhile without feed.

sorry for the rambling, its 1 am.

Matthew, thanks for responding,

Yeah I tried to disperse the numbers throughout the tanks, just for ease on biofilters/water quality. Honestly, I have not seen active eating since I got them. Well I had to end my first trial of research due to death rates, they are back into the 1000L tanks (holding) now. I did have 5 fish/190L tank when the trial was going. So would you suggest to stock at a higher density? I know water temp also plays a role with breeding, should I drop the temp a little?

matthew ferrell said:

One thing is that your stocking density is really low.  When tilipia go into reproductive mode they stop/slow eating.  So coupled together all this new found room to claim as their own space and your going to have non eating and fighting fish.

I am also not sure that the nitrite might not have them feeding. 

I traveled across state with mine too, and they ate the same day.

What to do is based on the project at hand.  What are you going to try and accomplish? 

If they don't want to eat, don't push it.  They can go awhile without feed.

sorry for the rambling, its 1 am.

High stocking rates, and warmer temps.  I keep mine at 76.  What is your research question?  If you have replication, you shouldn't have to end a project due to death. 

Also starting with 1 pounders might not be what you want to work with.

Remember the simply rules of fish health.  No feeding means either fish are stressed or sick.  If they are sick they will die, and if they are stressed they will get sick.  You need to find the stress-or, which I believe is multi-pronged at the moment.

I just split the population between two tanks, so I have 18 in one and 17 in the other (1000L tank). Well I am wanting to see if there is a significant difference in sweet basil yield between f blue tilapia and channel catfish effluents, as well as general hydroponic series. So pretty much seeing what nutrient source will give me the best plant yield. I will only use each species once. I have 6 small aquaponic systems, rearing tanks are 50 gallons. 

Hopefully stocking at a higher density will work. Thinking back to my trial, I had one 50 gallon rearing tank with 6 fish in it. I never lost a fish out of that tank or had any nitrite spikes.

If I can not get a handle on this, I may try to trade a local for blue gill. I will need fish within 3 weeks.



matthew ferrell said:

High stocking rates, and warmer temps.  I keep mine at 76.  What is your research question?  If you have replication, you shouldn't have to end a project due to death. 

Also starting with 1 pounders might not be what you want to work with.

Remember the simply rules of fish health.  No feeding means either fish are stressed or sick.  If they are sick they will die, and if they are stressed they will get sick.  You need to find the stress-or, which I believe is multi-pronged at the moment.

So I tried feeding my blues a various diet this weekend to see what they would eat.  Everything on the following list was consumed:
PeachesBread
Tetra feed
Mum flowers
Rye flowers
Greenbeans
My fingers(okay they just nibbled those)
artichoke leaves
paste, with and without sauce

I don't think its the feed.  how long did you cycle before those fish went in.  How much feed was on the bottom after a feeding?  Did you take the feed out or leave it in.



Ryan D said:

I just split the population between two tanks, so I have 18 in one and 17 in the other (1000L tank). Well I am wanting to see if there is a significant difference in sweet basil yield between f blue tilapia and channel catfish effluents, as well as general hydroponic series. So pretty much seeing what nutrient source will give me the best plant yield. I will only use each species once. I have 6 small aquaponic systems, rearing tanks are 50 gallons. 

Hopefully stocking at a higher density will work. Thinking back to my trial, I had one 50 gallon rearing tank with 6 fish in it. I never lost a fish out of that tank or had any nitrite spikes.

If I can not get a handle on this, I may try to trade a local for blue gill. I will need fish within 3 weeks.



matthew ferrell said:

High stocking rates, and warmer temps.  I keep mine at 76.  What is your research question?  If you have replication, you shouldn't have to end a project due to death. 

Also starting with 1 pounders might not be what you want to work with.

Remember the simply rules of fish health.  No feeding means either fish are stressed or sick.  If they are sick they will die, and if they are stressed they will get sick.  You need to find the stress-or, which I believe is multi-pronged at the moment.

 

Just some thoughts:

Don't you need to run them concurrently?  If you have 9 systems you can do this.  2 reps would be weak, but running them at different times would also be not the best. 

Are you going to have the same biomass to fish number.  Remember that fish at different ages have different efficiencies and oxygen demands. 

Had you planned on changing all the media and filters between each run, because some nutrients accumulate over time, and are not always available in the beginning.

So for my study I have 6 aquaponic systems. 3 of which are media filled and the other are DWC. I will run 3 trials, trial 1 will have blue tilapia, trial 2 channel catfish, trial 3 General Hydroponics Nuts. (so one nutrient source per trial). The trials will last  49 days. This study will be indicative of relatively small and new systems. 

There is a excellent study in regards to nutrient accumulation and yield over time, which will be included in my thesis. After each trial I will clean out the systems, and let them soak in a hydrogen peroxide solution for >6 hrs (including biofilters). 

I will try to have the same biomass per tank/fish number. I plan on re engineering the biofilters. There was too much flow in them, so I am going to try to mimic Dr. Lennard's biofilters from his studies (wet/dry). I will keep the existing filter media (bioballs, bactitwist, ceramic beads, and scrubbies) as well as filling up the 5 gallon container with scoria. I will also add a polystyrene cloth to the top. 

For the first trial I did not collect the fish food. This time I will. I will allow the fish to eat for 30 mins, after I will go back and collect left over floating feed. I allowed the systems to cycle for 2 weeks. I followed instructions from the Aquaponic Source as well as the products themselves (nitrifying bacteria and ammonia chloride). I assessed the ammonia, nitrite, and nitrate levels and they were at the recommended levels before I added the fish.

I do have very hard water where I am at. I am using General Hydroponics pH Down, which could have harmed the bacteria colonies due to the acetic acid in the pH Down. I may try to switch to a food grade phosphoric acid.

so in the past uneaten food stayed on the bottom.  I am trying to figure out you nitrite issue.

I've been starting an aquaponic grow and I was planning on using blue tilapia. I was wondering how your study went and if I could possibly have access to it. Thanks 

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