Backyard Aquaponics
A place to discuss aquaponics

Our aquaponic system has been flushed since 29 December and "test" plants have been added 3 January. They are doing pretty well since the nutriticient levels are only now rising to acceptable standards. Fish have not yet been added. The system consists of a 1200l fish tank, 4 x 350l growbeds, 400l secondary fish tank and 400l sump, driven by a 5 500 l/hour pump. Local tap water's ph is about 7,8, water is degassed for at least 24 hours before filling up the system as necessary. Dependent on weather conditions 15 to 40 l per day needs to be added. The ph level is currently 7,58 and TDS is 490. 250 m. Seasol has been added about two weeks ago and during the past two weeks I added 100 ml Nitrosol (N8%; P2%; K5,8%) to the system
Record of readings:https://www.dropbox.com/s/44fbe1u8gwgnxe1/PH%20Record.pdf?dl=0
The first plants were added 1 February. Is this too soon? Any suggestions and reccomendations are welcome

Here is a link to some pics of the overall system on imgur : http://imgur.com/a/rc2YH

That's a nice neat system good job you two . I like the canopies although I probably would have a problem with them if they blocked too much light. In that location with the wall I think they are probably a necessity.

Cheers

Whats the preferred PH value of the water to start adding Fish? Anything between 6.5 to 8?

The main thing is to transition them from the pH and temp they are at, to the pH and temp of your system. Fish can handle a pretty wide range of pH's and some can take a pretty rapid change but it's better if you don't stress them this way. 6.0 to 8.5 would be fine and they can go higher and lower than this.

Ignoring the fish for a moment, roughly 6.0 to 7.2 is a good place to shoot for the system pH in terms of nutrient availability for the plants . If your pH is higher, the bacteria, once they get going, will drive it down (so most people just wait for this). If it's lower you risk having the biofilter crash. You can run the system at higher or lower pH's than this, you just need to do more supplementation.

The reason I'm telling you all this is that if you want to adjust the pH it's easier before you add the fish (as I mentioned though, it will come down and you don't have to do this). If you do it afterward the change needs to be more gradual..

Thank you for this very informative reply. Fish should go into the system this weekend. ph is currently 7.8.

That's a bit high and you can expect iron lockout. You can use chelated iron DTPA or EDDHA would probably work in the system water. Spraying the iron on the plants avoids the nutrient lockout issue in the system water (I usually do it this way).

Most systems come down in pH within the first couple of months. Mine went for two years with the pH between 7.8 and 8.2 so it's possible to grow at the higher pH's but not quite as simple. I sprayed Maxicrop plus iron to take care of the iron problems I encountered. The same iron added to the water in the system would not have worked since it's not chelated.

I doubt you really need to but if you decide you want to adjust your pH down, shoot for around 6.5 to 7.2 and do the change using Hydrochloric acid (aka muriatic acid). It won't take much, this is a strong acid (observe all the appropriate precautions). You can get an idea of how much by doing the adjustment on a small portion of the system water (a few gallons in a bucket works). The amounts used should be proportional to the volumes that you're adjusting. Using the amounts you got from the test you can get a rough idea how much acid it takes for the entire system. Since I just figured something similar for someone else in another thread, this is how you'd do it -

A1 = Volume of acid needed to adjust pH of test batch to desired pH level
V1 = Volume of system water used for initial test batch
A2 = Amount of acid needed to adjust entire system to the desired pH level
V2 = Volume of entire system

A2 = (A1 x V2)/V1

Just plug in your numbers and solve for A2

Thanks a mill Scotty!