Backyard Aquaponics
A place to discuss aquaponics

The PH when the system was started 3.5 weeks ago was 7.6 and today was 7.2
Over the first few days of operation the water temperature ranged between 10 - 17deg, so I decided to try 2-300watt heaters in the system to speed up the cycling process, not expecting them to make much difference, but they did and temperatures now range between 16 and 19deg.

GH won't directly affect system pH - it's measuring the amount of Calcium and Magnesium ions. I know koi are not happy with very hard water. You'll see slow growth and skin problems over time. And you could have problems with scale deposits in the tanks and other plumbing. I'm new to aquaponics, so I don't know the effects on the plants, but I know that soils with high Ca++ and Mg++ are very difficult for plants to live in as they make it hard for plants to take in other nutrients. Are you certain it's the gravel? What is the GH of your source water?

Limestone, being calcium carbonate, will increase both GH and KH, so I don't think that is the issue since your KH is staying put and your pH is staying low.

My bad... I mis-read it as carbonate hardness (kH) had increased...

You are correct Madrone... general hardness is a measure of Calcium & Magnesium ions.... both of which are generally good, and essential for plants....

Nutrient lockout... and even scale buildup... are more a factor of pH... than just general hardness in itself...

Your pH levels are fine at this stage Mark... and will drop as the system matures... which in itself will allow the uptake of all trace elements... including the Calcium & Magnesium....

I don't think you'll have any problems.... and Australian native freshwater fish have become adapted to a wide range of pH and hardness conditions... and have vastly different tolerances to Koi and other ornamentals...

I have proved it to be the river stone by testing other fish tanks I have, one using this particular gravel, which also has a high GH reading. Tap water is 125.3ppm as were all other fish tanks using this water except the one with this gravel which was 232.7ppm. Anyway if Rupe is right it should be a good thing down the track further?

Hi Aquastud,

Rupe is spot on. I've had riverstones as my main growbed media for two years now. Once my system settled down the PH has not change much from 7.4. I also added about 50kg of shell grit as a buffer just in case.

Your system looks great, keep up the good work,

God bless, froggo.

I am treating my systems as experimental hobbies (I may do one on a commercial scale one day) and my original plan was to do two systems along old raised garden bed, 1-enclosed in a green house type enclosure and the other outside. I am now wondering weather to just extend the current system right the way along, or are green house style systems really worth all the extra effort? I realise temperature control will be better, but by how much? And i suppose you would have less pests attacking plants? Any comments or suggestions?

System up-date

System has been running now for almost 4 months, PH has remained at 7.2, Nitrates rose to about 40 and now with plants going well has dropped to about 5.



Have still got to install one more growbed over fish tank on this system.

I have noticed the broccoli are growing better in the growbed with riverstone compared to the one with hydroton, might be because it can root better in the heavier media?

Depends on your winters. I was more worried about summer cooking stuff before i was ready to eat it with mine. Perhaps just a shadecloth "roof" along the fence.

Looks like its trotting along nicely aquastud, well done How are the fish doing?

System up-date
I have finally finished the 1st system and commenced the 2nd.



I will be enclosing the first system once I finish the second one.
I was having trouble with fish dying in the first system a couple of months ago and thought a salt treatment I put in the fish tank to treat the fish flashing was the cause, but after extensive research I am not sure whether this was the case? I have only done periodic partial water changes since and fish have been fine.

The 2nd system will consist of 1 - 1100L fish tank and 4 - 500L growbeds and will be controlled from 1st system control box.





I use timing charts to work out programs for pump run times



All of my grow beds operate on independant timed flood and drain cycles

The control system gives me flexibility on how the system operates and I will be testing different methods for system efficiency and performance.



Because I have a separate pump for each growbed, I can operate each growbed with a different method. In the above chart the first growbed will be the standard 15 minute flood and 45 minute drain and the others cyclic flood and drain. With the cyclic flood and drain, I set the pump run time 30 seconds past the bell siphon start and the off time must be longer than the growbed drain time. By staggering the pump run times for each growbed I can keep the fish tank water level higher.

My PH has dropped to 6.6 from when I last tested it 2-weeks ago, it has been at 7.2 since june last year. The KH has been slowly dropping over this time and is now close to zero. I am wondering whether I should add some buffer (sodium Bicarbonate) or put some shellgrit in the system or do nothing? I know some people run their systems with low PH, but is this a good idea?
My system has been going well other wise and in particular one cherry tomato plant which has been going bererk, I have picked about 500 tomatoes so far of this one plant.

Some shellgrit (Calcium Carbonate) in your growbeds... or in a bag under a water return... will act as a self-regulating... slow release buffer...

Or you could let it fall a little more... then use some EcoRose (Potassium BiCarbonate) to buffer the pH... while giving anything that's flowering/fruiting.. a boost...

The latter is a strong buffer... and you don't need more than a teaspoon in 1000L at any one time...