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Discovering the Mosambique Tilapia.

There are several species of tilapia, the O. Mossambicus being only one of them; but it happens to be one of the two legal species to raise in California, the other being the O. Hornorum. The “O” stands for Oreochromis. Oreochromis is a large class called “genus” of tillipine cichlids which are fish endemic to Africa. Members of this genus, as well as those of the genera Sarotherodon, share the common name "tilapia". So the first thing we learned about raising tilapia is you have to do your homework and determine which (if any) species is legal in your state and /or county.

It seems there are a lot of politics around this fish; which is a non-native fish everywhere except Africa, its home of origin. The Aquaponic farmers in most of Australia are bemoaning the fact that no tilapia are legal there either (not even one species) so we didn’t feel so bad when we discovered we could only choose among two of the 30 plus species in the genus in our home state of California.

It seems the Mosambique has been in California for so long, it’s now considered indigenous (at least south of the Tehachapi Mountains). Significant worldwide distribution of tilapias, primarily Oreochromis Mossambicus, occurred during the 1940s and 1950s. So by the mid 1960’s, when hydrilla weed started clogging California irrigation channels, it wasn’t a big stretch to bring in Mosambiques to abate the invasion. They did their job and slowly found their way to the Salton Sea. There they thrived in the saline waters as this hardy species can be raised in both fresh and salt water. In the fish world, they call this trait “euryhaline.” Fish that are exclusively limited to salt or fresh water are called “stenohaline.” At this point in time, however, only the toughest euryhaline Mosambique can survive in the over saline Salton Sea.

In general tilapia are being farmed in large numbers around the world ranking sixth among all farmed fish. They are very important for their food value both to humans and other carnivorous fish like salmon.  When one genus of fish is fed to another, the one being eaten is called “forage food;” and tilapia rank high in that category.  But they have also become known for what they can contribute alive like their ability to control aquatic weeds, algae and clean up waste-water treatment run off as they are omnivores and can survive on just about anything including waste.

Although tilapia have had a bad wrap and are still banned in several states in the US and other countries, they are slowly demonstrating their importance as both a high protein food source as well as in aquatic maintenance control. As food shortages grow around the world, and aquaponics becomes a household word in America, we see a time when these bans and restrictions on tilapia will of necessity be reevaluated and even lifted.

How Do Female Mosambique Produce Mostly Males?

Because mixed populations of tilapia, male and female, mate with great abundance, an aquatic farmer can loose control of his situation quite quickly and end up with way too many youngsters who take up too much room in the aqua farm whether it be a pond or a tank causing slow stunted growth among the adults.

One of the solutions for this problem is hybridizing two different species within the genus to create females that produce mostly males. This is done by crossing a male O. Hornorum tilapia with a female O. Mossambicus tilapia. The O. Mossambicus has XX chromosomes and the O. Hornorum male, ZZ chromosomes. Because the Z chromosome is dominant over the X, the resulting offspring are all ZX, which is male.

The plus side of that arrangement is you no longer need to worry about over population in your aqua culture system. The downside is you no longer have a pure strain of O. Mossambicus tilapia or O. Hornorum tilapia. You have a hybrid strain.

What Are Some Of The Other Popular Tilapia Species?

Two of the tilapia species that kept coming up as we searched for our fish were the Nile and the Blue Tilapia.

The scientific name for the Nile tilapia is Oreochromis Niloticus. Whereas the O. Mossambicus came to the US in the 40’s and 50’s, the Nile tilapia didn’t come on the scene until 1974 when it was introduced to the US from Brazil.  By 1978, the Nile tilapia arrived in China and China soon became the world’s tilapia farming nation producing more than half of the world’s tilapia production from 1992 to present with mostly Nile tilapia.

One of the advantages to raising Nile tilapia over Mosambiques is their ability to withstand cooler water temperatures. Another is their delayed sexual maturity coming into their breeding cycle at 5 or 6 months of age instead of 2 to 3 months.

The scientific name for the Blue tilapia is Oreochrmomis Aureus. They were introduced to the Gulf states in the 80‘s for weed and insect control. Blue Tilapia can be found in Florida, Alabama, and Texas, although Alabama winters often do not allow survival of most populations. It very well may be that in those states, the Blue Tilapia is now considered indigenous just like the Mosambiques in parts of California. For aquaponics farmers, the Blue Tilapia is the most desirable of the genus precisely because it can survive in much cooler water than the other species.  If you remember from the Water page, the plants like the water cooler than the tilapia like it so you need to come to a mid-range between the two at around 72-74 degrees F. For Blue Tilapia that’s just fine. In fact, they can survive in temperatures all the way down to 48 degrees F although they will not grow fast or thrive at that very cold temperature.

Among those in the know, the Blue Tilapia is considered to be the best tasting of all of the Tilapia species. It yields very white, semi-firm fillets and has a great mild taste.  If Blue Tilapia are legal in your state, these are the fish to put in your aquaponics tanks; and here’s the best place to get them. 


Get your Blue Tilapia here! Click the fish.

We now sell Pure Strain Blue Tilapia that are known to be cold water resistant and delicious. We also have Mosambiques, White Tilapia and other Tilapia species.  Just click here or on the fish to Go directly to our new Live Tilapia For Sale Page. 

What Are Sex Reversed Fish?

Because many fish farmers don’t want to deal with the breeding brooding issue, several ways have been devised to skirt this issue. I’ve already discussed the hybrid method above. Another very benign way to control breeding is to separate the sexes by hand called “hand sexing.”

But starting way back in the late seventies, when it became obvious tilapia were not going to perform well as a food source fish because of their prolific breeding that was causing poor performance in closed captive situations due to over-crowding, marine biologists started exploring the various methods of sex-reversal.

Sex-reversal is exactly what it says, a way to turn a potential female fry tilapia into a male through the use of testosterone. Because recently hatched tilapia fry do not have developed gonads it is possible to intervene at this early point in the life history and direct gonadal development to produce monosex populations. Steroids given in their food during the gonadal development period can control the phenotype overriding the expression of the genotypically determined sex. This process is commonly referred to as sex reversal.

Methyltestosterone is the most commonly used androgen to direct the sex of tilapia. Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics. Various protocols regarding dose rate and treatment duration have been evaluated. All depend on hormonal treatment with sexually undifferentiated fry. Other, rather bizarre sounding experiments to replace the methyltestosterone with a natural form of testosterone have been tried with varying results. For example frozen bull testes added to the fry food did not work to create mostly male tilapia; but Haylor and Pascual (1991) reported successful tilapia sex reversal using ram testes as a source of dietary testosterone. The common method used today is a methyltestosterone additive in the food. The upside is tilapia have become the sixth most popular farmed fish in the world. The downside is the widespread use of large quantities of sex reversal hormone in hatcheries may pose a health risk to workers (Mair, 1997) and there is little information on the fate of the hormone in the effluent and ground water.

Is the use of methyltestosterone safe for tilapia consumers? The standard answer is this: “Studies have shown that 5 days from withdrawal of the hormone feed, the levels of the male sex hormone in the treated fish return to normal indicating that no residues are present. With several months from the time of withdrawal of hormone feed to the time of consumption of the treated fish, consumers are assured that the fish are absolutely safe for eating.” We haven’t seen those studies nor do we know who’s conducting them. We do know that Whole Foods began banning testosterone in fish about three years ago, searching the world to find fish farms that did not use the hormone. They even had to stop selling tilapia for a while before working out arrangements with farms in Ecuador and Costa Rica. "We decided not to allow the treatment of any fish that are ultimately going into our seafood cases. We don't believe that the hormone treated fish really meet the expectations that our customers have." Brownstein said.

Pure Strain Tilapia are Kosher.

According to Kashrut.com and the Jewish Orthodox Union, true pure strain tilapia are a clean Kosher fish. Mr. Jim Knott has an inquiry out as to what these organizations feel about tilapia that’s been genetically engineered  or sex-reversed; and I’ll report on that when I hear from him.

One word of caution, unless you’re raising your own tilapia, a strict Kosher eater should make sure he can identify the fish he is eating by purchasing it from a reputable Kosher store or by visibly seeing the fish with it’s skin on in order to determine that species substitution has not taken place.

What To Feed Your Tilapia?

Tilapia are omnivores; and, therefore, have the ability to eat just about anything. They love worms and here at Aquaponics USA, we’ll soon be adding a compost heap which we’ll be designing as per instructions from a handy little book called “Worms Eat My Trash”. But they’ll also eat lawn clippings, weeds and even other animal waste. We don’t plan to feed ours any animal waste. In fact, the fish food we found after much research doesn’t have any terrestrial animals in it at all. We discovered the same fish food supplier as the one used by that well-known US organic chain called Whole Foods mentioned earlier. Thanks to Whole Foods, this terrestrial animal free fish food exists as they insisted on not having their farmed fish eating cows. We all know about mad-cow disease by now; but what we don’t know (most of us don’t know it), even though the US stopped feeding cows other dead cows, they kept feeding dead cows to fish and chickens. The Fish Food company we’re using is called Rangen Inc. and their mill is in Idaho. The Rangen Corporation is dedicated to high quality feeds, and they are always looking to improve on their products.

How Many Fish In A 120 gallon Aquaponics USA Food Forever™ tank?

The question of fish to water ratio is a little tricky to answer. The fish produce waste, mostly in the form of ammonia. This must be converted into nitrates which the fish can tolerate in greater quantities. The conversion takes place in the bio-filter/grow beds in the Aquaponics USA system. A two grow bed system can convert twice the ammonia to nitrates as can a single grow bed system in the same amount of time.

The nitrate generated by this process then must be absorbed by the plants or it will eventually overwhelm the system and poison the fish. This requires plants of some size to be in the grow beds. The less fish poundage, the less plant mass is required. In addition, different types of plants of the same size absorb nitrates at different rates.

There are no hard numbers to answer this question but we can give you some ballpark numbers. If there is enough bio filter and enough biomass and a variety of plant types, then you can support one pound of fish for 2 gallons of water. On the other conservative end of the scale, you can support one pound of fish for every 10 gallons of water.

We suggest for a fully functioning and grown out single grow bed system, one pound of fish for every 5 gallons of water. That’s a middle of the road number. For a two grow bed system fully grown out with plants, one pound of fish for every 3 gallons of water. These numbers are maximums. Best to be more conservative as the system will be more stable with less chance of losing fish. As a general rule, beginners should stay on the side of less density. You can always increase your density as you become more experienced.

For lots of great information on the rearing and feeding of Cichlids, the fish family from which Tilapia come, you can get this informative book.

How Female Tilapia Brood Their Young.

Female O. Mossambicus are Mouth Brooders, which means they carry their eggs in their mouths to make sure they get lots of oxygen as the water swooshes through her mouth. Even the little fry spend a lot of time inside their mother’s mouth. Watch this amazing Video of a female Mossambicus with her fry.

Our 125 Mosambique Tilapia are swimming around in all five of our fish tanks (this one has the web cam). It’s a 320 gallon Tank with our biggest Tilapia and their offspring born in November 2011.

This Webcam takes you up close and cozy with growing, thriving Tilapia. This tank used to have our small Tilapia in it; but they aren’t that small anymore. If you’re viewing this page at night, you’ll have to come back tomorrow in the daylight.

Mating Habits of Tilapia.

Tilapia come into sexual maturity at about eleven weeks old, which is several months before they are fully grown out (1 lb. or so). Once they reach sexual maturity, they spawn about every five to six weeks so each female can produce 200 to 300 mixed sex fry at each spawn. That’s a lot of fish. These are natural, sexually active fish so raising them means taking responsibility for their offspring or controlling their breeding. If you have a one-tank backyard system, it would not be wise to allow your Tilapia to breed wildly as your tank would soon be overrun with fry leaving no room for mature fish.

Therefore, we recommend that for your first fish order, you get hybrid fish, which, as explained above, are fish that are naturally all male. The male tilapia is larger and grows faster than female tilapia, which will help your system mature faster as well. Besides getting a mature system faster, you can concentrate on learning aquaponics without the added responsibility of breeding tilapia.

We are developing a hatchery system product, which we will be adding to our product line that you can order and connect to our Family Systems, the FFGS-20, 40, 50, 80 and 100. This hatchery system will allow you to breed your own fish. We are about to start breeding our own fish and will soon have a Fish Breeding page up on this website to give you all the necessary information about tilapia breeding. If you choose to raise another species of fish, you will need to research the breeding requirements for that fish.

Looking to Buy Tilapia? Go to our new Live Tilapia for Sale Page.