Pond Boss Forums GENERAL QUESTIONS Help My tilapia are biting the dust

The stocking density here is a testament to how tolerant Tilapia are of bad water quality!

I see filtration of solids, and frequent removal, yet till filters are cleaned, there is no bio-filtration to break down the rapid spikes in ammonia and nitrite levels. If the 700 gallon tank is outside, the recent, very cool evenings are wreaking havoc on the Tilapia's immune systems as well.

Tilapia do not have a "normal" stomach, so even a couple days of not eating will cause a sunken look. The green slime is normal digestive juices and bile from digesting fat stores in the body when not eating.

I would suggest changing out ALL your water, twice, immediately to get rid of the high ammonia and nitrite levels I am sure exist in the "pond".

The old adage of one inch of fish per gallon of water for the ornamental aquarium industry simply doesn't apply for fish farming. I used fluidized bed sand filtration for my bio-filtering and routinely housed hundreds of inches of fish per gallon. My main aquarium when keeping fingerlings for Aquaponics supply would have ~7000 inches of fish in 150 gallons of HIGHLY filtered water.

Below was a "typical density" of fish in my aquariums...probably ~3000 inches in 150 gallons. (Note all fish have a "sunken" belly, but are exceptionally healthy)

Rainman, I do have an IBC tote that is my bio filter with bio balls and other plastic matter. This tank or "pond" what have you, is indoors. Stays right around 75-85 degrees inside all year.. I have radiant heat in the concrete and that alone heats the tanks in the winter, so that's nice. What kind if sand filter do you run? I also do about 1/4 water change on a daily basis which I believe has been keeping the ammonia and nitrite at bay. It's apparent to me that I need more oxygen to both my bio filter, along with the fish. Hetero and aerobic bacteria need oxygen just as much as my tilapi do.

Sounds like you run high densities, additionally what mechanical filtration, and aeration do you have for those critters?

Not advocating pushing the limit but you can go quite a bit higher in cc with the right equipment Rainman says.

And just so you know, you were absolutely correct on your rule of thumb for aquariums and I didn't disagree. It's just that although similar, aquariums and recirculating systems have different goals, as do koi ponds which are also basically small scale recirculating systems.

Oh yeah I didn't take it that way at all. I really didn't think about the fact that some folks out here are raising as many fish as they can for resale "duh" on my part..... Never even corssed my mind when I said what I said, but like you said you better have your ducks in a row if your going to try and push it hard like you guys do! One wrong little thing and it could end up a mess....

CCF keep us posted.

RC

I have back up power and will be installing an audible alarm on my linear air pumps if they fail so it's not too scary. I'm slowky converting all my systems to air lifts so there will be no need for water pumps which can result in failed pumps. You need to think like NASA -- back ups! Also one usesmuch less watts just using air lifts so back up power lasts longer not to mention saved money.

A neat phenomenon takes place once you get your fish density up to .25 lbs. per gallon-- a better feeding response. It becomes competitive and the fish become eating machines and actually grow faster!

I'll tell ya what all this sounds like!! A LOT OF WORK!!! No wonder these fish are so expensive!! I don't think the average Joe really understands what all goes into what you guys do!! Lot of work for sure!

RC

My system was not designed for growth. I actually needed to inhibit growth as much as possible with minimal feedings, minimal "safe" water temperatures also.

I used several Magnum Pro non-bypassing power filters, a 40 watt UV chamber and a Pentair 9FB Fluidized Bed sand filter. Filtration was handling 150 gallons, but designed for 900+ gallons of "normal" use.

I was never a fan of bio-balls as they clog badly and the dead bacteria film inhibits new bacterial growth by covering needed substrate. the same goes for bio-wheels or any variation of them. They just need too much cleaning for me. The fluidized sand filters are self cleaning and the substrate surface area to footprint is unmatched.

I would NOT consider the solids filtration I used as a good way for solids removal, but my fish were in the basement next to the wife's office. She HATED the hatchery smell at first, but once she began seeing black ink rather than red while doing the company books, the stench in her office became MUCH more tolerable! lol

25% daily water changes are okay. I never bothered changing water daily. I Changed it entirely weekly, or if the fish showed signs of stress, then I changed it all out, twice. Partial changes never eliminate water quality issues, they only delay and briefly reduce them.

Agreed Cecil! My Tilapia looked like a tornado forming when I walked in a room. When feed was tossed in, the frenzy was insane with water splashing everywhere! A cup of 1/16" pellets would disappear in seconds! In low density, feed could sit for minutes while being leisurely eaten.

Rex,

The five moving bed filters I've built out of blue plastic drums using mb3 media from WMT in Baton Rouge are self cleaning as the plastic media just like your sand is in constant motion. However as with any biofilter except for polygeysers, it's important to get rid of as much solids as possible first isn't it? That way you don't have heterotrophs out competing the autotrophs and creating anoxic conditions in you biofilter.

I built an upflow sand filter 6 inches in diameter identical to one sold by AES / Pentair complete with a clear pvc top section to keep tabs on the sand, but as if yet haven't used it. I was told about a few disasters that occurred with them which scared me off. I was also told they need constant attention and are really touchy.

You had no issues?

Here's the plastic media:

http://www.w-m-t.com/Products/WaterTek_MB3_Moving_Bed_Media.php

The sand filter in the designs mentioned ARE touchy! Flow is critical! Too much, and your sand flows right out, too little, and it doesn't go into a fluidized state. I placed the sand filter at the end of my flow loop, but solids wouldn't matter in it as there are no dead water areas to create any anoxic condition, and solids will either decay, or flow through.

FWIW, the media used is not regular sand. It is an angular material that is close to neutral buoyancy for easier fluidization, larger, uniform surface area and better cleaning when bouncing around in the fluidized state.

If I were going to design my own, I would make it conical in shape so that the upflow is so minor at the wide top, sand flowing out would not be an issue.

I just liked the sand filters because the surface area and self cleaning couldn't be matched in the same space/flow used. The media you use, Cecil, is good from what I have read, but to get the same surface area, you would probably need at least 100 times the space as the sand, plus, the inside parts could clog fairly easily, potentially creating the anoxic areas you mention.

Interesting. Yeah you can't match the surface area of sand or sand like material. What is this angular material you speak of? I know size of the grains is very important and even with the best of care you loose sand over time and need to replenish it.

Inside parts of MB3 DO NOT clog easily. They are constantly rubbing up against each other and the openings inside are fairly large. The media changes color over the years but no clogging. They are not as fine as Kaldnes which will clog over time.

Cecil, I'd beg to differ on the MB3 not clogging. Even the product info comments that only the outside is self cleaning and the inside is a "protected" area as quoted from Watertek....WMT’s WaterTek MB3 polyethylene media is robust, durable and bacteria friendly; With a specific density slightly below 1.0, the media fluidizes easily with air. MB3 delivers a self cleaning outer surface with plenty of protected inner surface area.....from expeience, that bacteria slime will completely encapsulate areas.


I can't find the more detailed information on Pentair's LifeGard site on the sand media design, but here is some basic info...... http://www.petco.com/product/8167/Rainbow-Lifegard-Replacement-Media-for-Fluidized-Bed-Filters.aspx

Well we'll just have to disagree Rex. All I can say is I've been using it for 2 years now and it's not clogged yet. However I do run the water through my clarifier before it gets to the biofilter. All the literature says you want the water to be as clean as possible before it hits your biofilter, even sand filters.

Did you run the water through a filter first? If so what kind of filter?

IDK about the literature. The FB filters can be separate from the solids removal system entirely. Any solids light enough to be drawn in by the fairly low flow/suction will flush right through as they are for bio-reaction only, not filtration.

In my big tank, the FB filter was fed bypassed return water that had first been run through 3 Magnum 60 canister filters set up in parallel, then run through the UV sterilizer.

Below, are some pics of the setup being used for show and planted. In the first pic, you can see the 3 filters and the UV Sterilizer in the back (on the wall). the second has the sand filter hanging off the back of the tank in the background of the pic. The garden hose fitting and valve were for restarting the FB filter after a power outage or when stopping flow (the one drawback to FB filters, restarts are a real pita!). Third pic was again, common fish density in the 150G aquarium. Fourth was when I had a few fingerlings of several species (CC, LMB, SMB, BC, BT, BG, HBG, RES, WE, YP, GS, FHM)

Thanks fir sharing Rex.

I bought a UV filter once for my outdoor aquaponics system as I thought I would be dealing with FA. Never have and have never used it.

In the process of cleaning the water, do you guys have to physically clean some kind of filter every day? Would you have to do this with whatever system is used: Rex with your 3 canister filters, and Cecil with your clarifier?

Fish, I fed less to slow the rapid growth in Tilapia, so I only had to clean filters when water flow was reduced, but normally, daily (or more often) cleanings are needed.

Rex,
Reading through this thread has convinced me that when it comes to Tilapia, you're a lot more than just another pretty face!

Yeah he knows his stuff for sure!!

RC

Thanks Rex. And what these other guys just said is sooooo true. I have been messing around with a few pond type fish in an aquarium to help me learn a few basic things you guys talk about with these systems. I learn best by doing....Wow, one thing is for sure, there is a lot to it that you guys just take for granted as part of the job and do, and think nothing of it.

Do your tilapia spawn, even though you may not be trying, when they are in such high densities as you show?

I used to have spawning, rearing and holding tanks, but the demand outpaced the reproduction volume I could do in my home pretty quickly, so I began having someone handle that for me.

The fish don't spawn much in high density situations, and any eggs females lay are gobbled up by other, hungry fish as soon as they are laid in crystal clear water.

Thanks for the kudo's on "what we do", but it is like any job people are used to doing....Some of us are blessed that it happens to be a passion for a lot of us as well!

Well here is the scoop. It's been almost a week, and believe it or not, I haven't had a single tilapia fatality. Lol. I have nile, Mozambique, and blue tilapia together. The only fish that were having a tough time was the Mozambique. But with a few minor changes and plumbing to make the water more turbulent when returned to the fish, I think I gained some oxygen. However my system does need evolved more. It's been changed around more times in the past two years than I've changed clothes.. Ehh I'm just kidding. But, on a serious note.. It would be nice to convert to a sand filter, and get rid of that behemoth of a bio filter; the one with the bio balls that get all gummed up.. But, I have a question. I have oodles of hydroton that I bought a while back, that could fill a 55 gallon drum. I was thinking about making my own gravel/ sand filter out of poly 55gal drum; for I have an abundance of those as well. Should I, have two in sync with each other, the first being filled with hydroton, then the second filled with sand? Or fill half and half of each? I could be getting into a quandary doing this, for Rainman said that sand filters are touchy when it comes to flow rates through them.

Have in mind, using a 1/3 horse pump. Two inline gravel filters might be too much.. Bear in mind also, I have a volume of 900 gallons, of fishy water. I thought I had 700 before, but I was mistaken. Solids are removed on a screen, then into a house water filter, then would continue on, into the sand/gravel filter..

Cooncreekfish,

If you filter out your solids before going to the biofilter you shouldn't have any issues with the bioballs gumming up or whatever you use for a biofilter. It's one of the main precepts in recirculating systems to clean the water BEFORE going to the biofilter. Otherwise you can have anoxic conditions in your filter in all that gunk, and your autotrophic bacteria is competing with heterotrophic bacteria that prefer those conditions. And the heterotrophs have a big advantage over the autotrophs as they mulitply a lot faster. You'll also get bad odors if your heterotrophs are king of the hill.

Here's a pic of a piece of Mb3 media in my moving bed filter that has been in use for 2 years. As you can see there is no clogging.