If there was such a thing is a prince of fish in Aquaponics then the Barramundi would have to be it.
Think of a fish that has no fear and if you were shrunk down to it’s size  – it would probably eyeball you for a moment then lunge and eat you whole in one gulp and not give a second thought about it! An awesome fish the Barramundi and many people that grow this fish species love watching them feed because when they are hungry – they really slap the water with gusto. Check out the YouTube clip above of this large Barramundi dispatching a live gold fish in one bite! A cruel reminder of its predator nature.

Barramundi is an excellent table fish highly regarded in most  restaurants and a great fish for Aquaponics – but not recommended for beginners. Well, thats what I heard – so being brazen enough to grow out a heap of Jade Perch without difficulty we decided to give Barramundi a try. They’re a warm water fish and do exceptionally well in temperatures above 24 degrees centigrade. See the chart for an example of what grow out size you can expect – in optimal conditions!

Barramundi Growth Chart (Click for Larger View)

Whats so Great about Barramundi?
Barramundi are reputed to be fast growers according the the Australian State Government handbook on Barramundi, “The Barramundi Farming Handbook”. Imagine growing a half kilo Barra in 5 months, or a 1 kg Barra in 7 months or 2 Kg Barra in 12 Months?

How could these figures be possible? Spectacular growth like that should make it an ideal fish for aquaponics? No wonder they are a preferred farmed fish in conventional aquaculture.

But there is a bit of a snag if you hope to grab a few of them and throw them into your aquaponics tank and think your job is done.

Why they are hard to Grow
Barramundi fingerlings need to be graded to survive. At fingerling size 4cm or an inch in length, kept in a tank – they will attack and eat one another. The larger sized fish will nip and wound smaller fish. You will notice the smaller fry fish swim about the tank with a chunk taken out of their sides. Eventually that fish will die if not eaten by the others.

Barramundi Fry are Cannibals

There’s a couple ways of dealing with this problem. Ideally you will need to separate the bigger fish from the smaller. Special cages are designed to allow the smaller fish to swim through the bars and escape the larger predator. The other way is through attrition. Buy a lot more Barramundi fry and expect half of them to be eaten. After all the surviving fish will grow a lot quicker on their high protein diet and you’ll soon figure out which ones are the cannibals by their increased girth!

The third option is to buy your Barramundi as larger juvenile. At around the 10-15cm size the fish will stop eating each other. This is probably the better option but slightly more expensive as larger fish command a higher price.

Water Quality
Barramundi are rapid feeders but along with that benefit comes a problem. What goes in – has to come out. Barramundi are big poopers and fouling the water requires adequate system to deal with water filtration. You may find that what works well with tilapia which are a very tough fish species – won’t work as well when dealing with Barramundi. Their water requirements are more stringent. You will need lots of dissolved oxygen going into their tank, supplying good aeration. Barramundi need very good water quality in Aquaponics and preferably water temperature between 26°C and 28°C. An ideal fish for Aquaponics if you live in the tropics. An expensive proposition if you live in a cold climate. Some people prefer to grow Barramundi over the summer months in an Aquaponics system. Eat them in Autumn as plate sized fish and then over the cold winter months replace them with cold water Trout. A smart idea if you can get both types of fish in your state or country.

Our experience with Barramundi
Here at Ecofilms we decided to grow some Barramundi in a conventional six foot fish tank that is housed in the lounge room over winter and then introduce them into the Aquaponics tank as water temperature heats up over Summer. This has meant heating the tank with a 300 Watt heater when the water temperature falls below 24 degrees. We got our fingerlings when they were very small and this resulted in a number of deaths due to the small sized Barramundi eating one other.

Barramundi enjoying the warmth of a 300W heater

We also learnt the hard way not to cut corners and cycle the system properly for at least a few weeks before introducing the fish. Warm water, high pH and an ammonia spike meant a few fish died due to ammonia toxicity. That lesson was well learnt. But the surviving fish are all growing at a terrific rate. Having them indoors over winter means you can feed them every few hours when you walk past their tank. They also let you know when they are hungry by their increased activity when you approach the tank. A sprinkle of  fish pellets has them slapping the water in a frenzy of activity. They certainly grow fast but probably not as fast as the stated growth rate in the chart above. Our plan is to introduce them into our aquaponics system when summer approaches and harvest them by next autumn. Thats the plan at least and so far its all working quite well.

Source: http://www.ecofilms.com.au/growing-barramundi-for-aquaponics/