Backyard Aquaponics
A place to discuss aquaponics

Howdy all,

Ive got about 50 TIlapia fingerlings in a 2000L tank....the only air pump Ive been able to get locally (will be buying a bigger one in a week or so) is a pissing little 2 outlet small aquarium job...only putting out something like 300Lt/hour. I know this is inadequate.

I have 3 points where water is slapping the surface, ie. the siphon (which bloody roars when its going), the SLO from the FT to the ST, then the return from the ST to FT....

Now, many of the Tilapia can be seen gulping at the surface after a feed...not all the time, just after a feed.

Is this normal TIlapia behaviour? or are the starving for O2? Ive never had Tilapia before coz they have always been illegal where ive been, so not used to them yet....


CHeers

Also, is there a general calculation or rule of thumb as to Lph of O2 delivery for x amount of fish, or is the rule simply as much as possible?

The gulping is from low DO levels. When they eat, they consume more oxygen and the DO drops. Thats when you see them come up to the top and start throating afterwards.

Lpm/lb of fish will depend on your water depth, type of fish and the type of diffuser you use (bubble size).
Using a standard medium pore diffuser at 3' water depth (and oxygen consumption rates for warmwater juvi's) you can expect to need 0.28lpm/lb of fish.

Cut the feed down and get as much air in there as you can , and as much splashing on the surface as you can

Thanks for the advise....seems to have worked.

I increased 'slapping' but putting an elbow onto my return to the FT, so now the water is coming out vertically (i.e. straight up, not directly down into the FT) which is creating much more of a splash and alot more obvious bubbling on the surface. Also reduced pellet feed and increase kang kong, which they seem to love....

No noticeable gulping in the last 24hrs...

Hi Floyd

I have kept Tilapia for about 5 years in Brunei (similar climate) I have rarely seen Tilapia gulping for air, only when the power goes off for extended periods do they do this.

On the other hand my Koi will gulp for air after the power is off for even 5 minutes and Barra will gulp air even if a pump is going and the water is a little dirty.

Tilapia are a pretty tough fish, I have seen them go without water circulating for a few hours and still survive. If worst comes to worse, I turn the hose on and suspend it from a great height if there's no power for an hour or two.

Dave

Check your nitrite reading. Nitrite will cause fish to appear like they are lack of air. But really it is the nitrite that inhibits oxygen to be transported by the blood.

Easy fix will be to add 1kg of sea salt per 1000 litres of water.

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