High PH and No Nitrates

[Ahren Spilker]

I have a single IBC Tote Aquaponic system. My tap water PH=7.5

The system cycled fish-less (added ammonia to kick-start it) for about 40 days and reached a steady PH of 7.0 and Nitrates exceeded 80ppm and ammonia was 0ppm.  I have about 7 tomato plants and three cucumber plants growing in the bed.  The tomatoes have reached upwards of four feet and have fruit on them already.  I had been adding one capful of liquid seaweed each day up until I put the fish in.

at about day 40, I added 40 fingerling tilapia 8 days ago.  Three days ago i noticed my water had spiked to PH 7.8,  and then today I checked again and the ph is still at 7.8, nitrates are at 0ppm.  

Is this normal?  Should I worry?

[Ahren Spilker]

Ammonia is 0ppm as well.

[Harold Sukhbir]

Hi Ahren,

Your top up/source water is PH 7.5ppm, so that's going to be your readings for now. Yes it will fluctuate as the system is new/"newish". With those nitrate sucker fruiting plants in a new system it will be some time for you to register much if any nitrates at all. When your fish start growing and eating more feed your system PH will start coming down and then your plants will grow better. Your existing plants may slow down the progress they showed earlier, until the fish "catch up". If you want to help things along and have the means you can keep on supplementing with seaweed extract. Newer systems do better when planted with leafy vegetables for the first 6 months and then the fruiting plants can be added.

[Jeffrey Ihara]

Would there be a problem with trickling in some small doses of ammonia, to compensate for what the leetle fish aren't making?

[Ahren Spilker]

Great, I was not sure if i could keep dosing with seaweed extract because I didnt want to harm the fish.  I have noticed a little yellowing on my cucumbers and wondered if it was because they were not getting enough nutrients.  I just started dosing with Iron Chelate as well, about a teaspoon per week.  

I will go back to dosing with a capful of seaweed extract as well.

Thank you for the feedback!

[Harold Sukhbir]

Hi Jeffrey,

Yes in theory you can dose with ammonia slowly increasing the amount to expand the bacteria. I don't think it will solve the nitrate problem with these types of plants though ( I can be wrong as i don't know all the system specs), and besides the more important thing for now is the building of minerals. Unfortunately there is very little in way of a shortcut for building minerals. I have experimented with an early AP system supporting it with Hydroponic inputs. There have been some noticeable gains by using these inputs but without proper testing equipment, you run the risk of upsetting the balance of the system and creating nutrient lockout problems.

Jeffrey Ihara said:

Would there be a problem with trickling in some small doses of ammonia, to compensate for what the leetle fish aren't making?

[Harold Sukhbir]

Hi Ahren,

Iron is a micro-nutrient and is only required in small amounts. The average for AP is 2ppm per system water volume. Adding too much can cause lockout for other minerals and even cause them to precipitate out of the system resulting in plants showing deficiencies. AP systems are different from Hydroponic systems and are over time, meant to develop more like naturally occurring ecosystems, keeping mineral manipulation of the operator to a minimum

Ahren Spilker said:

Great, I was not sure if i could keep dosing with seaweed extract because I didnt want to harm the fish.  I have noticed a little yellowing on my cucumbers and wondered if it was because they were not getting enough nutrients.  I just started dosing with Iron Chelate as well, about a teaspoon per week.  

I will go back to dosing with a capful of seaweed extract as well.

Thank you for the feedback!

[Vlad Jovanovic]

... "...a cap full of seaweed extract a day...a teaspoon of Fe-chelate per week..."?!?

If you don't mind me asking...how did you come to decide that those were the amounts that you should be dosing? 

[Ahren Spilker]

I got the capful of seaweed extract from Murray Hallam's Video on Aquaponics and the Iron Chelate from a formula from Brightgrow Agrotech, based on my volume of water I came up with about 11.32g of Iron Chelate 10% every three weeks but he said to cut he dosage to weekly so as not to shock the system.  11.32g is about 2.4 tspns every three weeks.  I basically just rounded for my comment.

Of course I am brand new with all this so am learning as i go.  Open to any and all help!

Thank you to everyone for their comments

[Harold Sukhbir]

Hi Ahren,

See you got a firm grasp on the chelate dosing!. I've used seaweed extract as a regular supplement in my AP for the past 3 years. I've done other systems without adding the extract and have noticed a big difference in plant growth. The seaweed i use is fresh from the ocean, does not contain added iron as the manufactured counterpart, and i dose approx. 5ppm/volume per month without any adverse effects this far.

[Vlad Jovanovic]

Very cool. Nate's videos and posts are always full of good info 

Most of the store bought MaxiCrop/Seasol/Kelpak type extracts have about the same TE (trace element) content as seawater, it's the auxins, and cytokinins (plant hormones) that they are extracting...So if you don't need/want the hormones, but do want all those TE's, it's much cheaper to use sea water...or dehydrated sea water (sea salt).

Ahren Spilker said:

I got the capful of seaweed extract from Murray Hallam's Video on Aquaponics and the Iron Chelate from a formula from Brightgrow Agrotech, based on my volume of water I came up with about 11.32g of Iron Chelate 10% every three weeks but he said to cut he dosage to weekly so as not to shock the system.  11.32g is about 2.4 tspns every three weeks.  I basically just rounded for my comment.

Of course I am brand new with all this so am learning as i go.  Open to any and all help!

Thank you to everyone for their comments

[Ahren Spilker]

I am using maxicrop seaweed extract.  I really like the results and as long as it wont hurt the fish, I guess i will keep using it.

Again thank you for everyone's comments!

[Harold Sukhbir]

Hi Vlad,

" it's much cheaper to use sea water...or dehydrated sea water (sea salt)."

Thanks!, very interesting, will look into it for sure!