A Community and Forum For Aquaponic Gardeners

Two questions

I started my aquaponics system in March with 15 tilapia fingerlings and added 20 more in April after the water was established.

1) The phosphate level in my tilapia pond runs about 8 to 10 which I think is high. Is this level harmful and what problems will it cause. The fish don't seem to mind as they are thriving and reproducing. Not satisfied with the veggie production though but it may be because I wasn't producing enough fish waster.

2) about how long is a 1.5 pound tilapia?

Thanks

Frank Scanlan

Coral Springs

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Replies to This Discussion

Permalink Reply by Viol8r on August 30, 2013 at 5:50am

1) could be a filtering issue.. how much grow media to gallons of water are you using? Are the rest of your tests (nitrate, nitrite, etc...) ok?

2) Depends on their gerth and height too, but 8-10 inches could definitely be a 1.5 lb fish.

Permalink Reply by Frank Scanlan on August 30, 2013 at 7:17am

I have about 450 to 475 gallons of water; and the grow bed is about 275 gallons. The ammonia and nitrite levels are good. I run the pump/flood every hour for 15 minutes.

Permalink Reply by TCLynx on August 31, 2013 at 7:12pm

Phosphate level of 8-10 ppm is really quite low for most plants. Or are you saying the phosphate level is 80-100ppm? IF that then maybe it is a little high. What is your Nitrate level? If they both really high, you need more plants or grow beds and more plants. If they are both only like 8-10 ppm then they are low and you could feed the fish more.

I can't really answer #2 so well since I grow catfish and they are often close to 18 inches by the time they reach 1.5 lb and can get to 3-5 pounds in 12 months in my systems.

Permalink Reply by Frank Scanlan on September 1, 2013 at 12:38pm

No 8 - 10 ppm.. I have the Pondcare Master test kit and it does not have a Nitrate test. it does test for Nitrites ( 0) and Ammonia (between 0 and .25) My PH has been close to 8 but I added PH Down from General Hydroponics and it is currently between 7.0 and 7.5.

I may not be feeding enough. And I do need to add some plants.

Thanks

TCLynx said:

Phosphate level of 8-10 ppm is really quite low for most plants. Or are you saying the phosphate level is 80-100ppm? IF that then maybe it is a little high. What is your Nitrate level? If they both really high, you need more plants or grow beds and more plants. If they are both only like 8-10 ppm then they are low and you could feed the fish more.

I can't really answer #2 so well since I grow catfish and they are often close to 18 inches by the time they reach 1.5 lb and can get to 3-5 pounds in 12 months in my systems.

Permalink Reply by TCLynx on September 1, 2013 at 12:55pm

A note about pond and aquarium test kits and recommendations. They want you to keep your nitrates and phosphates low because those would cause algae blooms and poor water quality problems in a purely ornamental system where you are just feeding the fish and having to do water changes to keep the levels from getting out of hand.

In Aquaponics, the veggies use the nitrates and phosphates so we actually want some of those for our plants. If those are 0 and the plants look great, then you probably have a perfectly balanced system and the nutrients are being used up only as fast as they are being produced. If the nitrates or phosphates are 0 but the plants are doing poorly and showing signs of deficiency on those, then you need to feed the fish more or get more fish. However if your nitrates or phosphates are really high (like off the chart) then you might need more plants or to feed the fish less.