FEEDING FISH: How Often and How Much?

[Kyle Sy]

Hi,

Newbie here. We just started our Aquaponics Raft System a few months ago, however we are still not sure when and how much to feed our fish. We feed them with pellets.

How often should we feed our fish? in addition, how much per feeding?

We have 40kg of Tilapia as of now.

Please help :) Your responses will be appreciated. Thanks!

Kyle Sy

Tagaytay, Philippines

[Kyle Sy]

Hi Joel,

Thanks again for a lot of useful infos. This proves that we still have a lot to learn! :) 

Yes, we are now trying to run another experiment with new adjustments and all of your recommendations. Now, without the coco coir. I agree with you that the system may be more complicated with this organic stuff installed.

The replacement of water and halting the circulation was only done because of the coco coir or the findings that we are losing fish quickly. This time, hpoefully, we wont need to press the emergency button :)

It was also great that you pointed out that circulation is very important for the fish and the plant, in this case, we really need to find an optimum or right levels and rates for our system to run it simultaneously.

 Thanks for the help everyone! we'll be more careful now!

From,

Kyle

Joel G said:

Hi, Kyle!

 

 "... If the system is not circulating, how many % of water do you suggest must be changed?" 

BFAR and SEAFDEC recommend (for a properly cycled and loaded tilapia system) a 10% to 20% weekly water change (as opposed to a daily 40% equivalent to 280% weekly volume). Please note that is a "general guide" or "baseline". More efficient filters (mechanical, biological and chemical) and sufficient aeration can allow you to increase your biomass (more tilapia per volume of water).

Vlad points out that you really should measure your PH (and probably hardness, ammonia, nitrite and nitrate) particularly when starting your cycle and/or adding a new component (like coir or even "fresh" water). In Cartemar, an API master test kit costs about P1000 and is good for up to 800 tests. 

I have to admit that we do not test either, but then we are developing/researching systems intended for low cost backyard aquaculture (in the PH setting).

 

 "... We used Coconut Husks to act as biofilters for the system. About half of the grow bed is filled with it. Our plants are placed on plastic cups that are floated by holed styro boards ...". 

Rereading your original post, I have to agree with RupertofOz that coir is usually not used, particularly for raft systems. They are probably best for wicking beds. He also pointed out that coir has a lot of downsides that you should be aware of (even though it is very convenient and virtually free for us in the PH). This was my point when I asked if you have scientifically determined the cause of your fish deaths, and only measurements can pinpoint for sure the said root cause (and thereby help you decide what to add/change).

By breaking the circulation between the plant and fish systems, you effectively have a separate raft-based plant system system and an aquaculture system, and lose the benefits of aquaponics. Raising 40kilos of fish while consuming 800 liters of water a day (40% of 2K liters) does not seem economical to me, so I assume you are now looking at other ways to reintegrate the plant and fish systems?

 

Regards,

- Joel