Backyard Aquaponics
A place to discuss aquaponics

I bought a system of a guy from gumtree which he had running for 18 months and i have cleaned the rocks and added all new water. He had 4 silver perch in it which i just had in a barrel changing the water everyday with an air pump but now I've added the fish to the system, It is based on a Chop2 system but with a 1300L ish tank. I have set up two of the three grow beds. And I have a high pH around 8.2 and I was wondering what would be the best way to bring down the pH?

The bacteria prefer a higher pH, so it will assist in cycling. I wouldn't be tempted to add acid to the main system, it's pointless, you will simply cause short term pH bounces, which the fish hate.

Treat any top-up water with Hydrochloric acid to a pH of 6.0 (and maintain it there) about 24hrs before adding it into the main system, this will consume the carbonates in the water so you're not constantly adding more to the main system, which in turn will allow the natural acids produced by the Nitrification process to overcome the carbonates in the main system sooner, leading to a natural decline in the system pH sooner.

Ok thanks well i don't nee to add any more water, so should i just let it run. And should i keep adding seasol? And is 8.2pH to high for the fish? What can they tolerate?

You will need to add top-up water from time to time, especially when you have good plant growth and/or the weather starts to warm up... about 10% per week is common, even 20% in some systems/situations.

8.2 is fine for the fish.

Another method you could use is to remove some water from the system each day, ie a 20L drum, treat it to a pH of 6.0 as described before, leave it sitting for a few hours, then return it to the tank. This will help speed up the natural pH decline in the system.

Seasol at 2-3 capfuls (30-45ml) per 1000L, per week, until the system is cycled and fish added, then back it off to 1 capful per week.

I could be wrong, but I was under the impression that over time, most AP struggled to keep PH above 7, or even 6.5. The fish might prefer it lower, but if they are happy, best to let it get there on its own. Rapid PH changes will kill them.

1 do you have plants in your system and what type?

2 are you using any filtration other than the grow beds?

3 you need plants in the grow beds for them to filter,

A high PH is good for bacteria and the fish don’t mind it in the high 7.4 range, your plants would like it more in the 5.5 range,

I am running a chop2 chift pist split flow system,

don’t panic!

I have got onion, strawberries, broccoli, lettuces, tomatoes and snow peas.
I also have a radial flow filter and i have the water running into the grow beds through a little scrubba which picks up a bit of the dirt.

Then you will have a potassium shortage soon, tomatoes need lots of potassium! And you wont have enough to feed one plant in your system until its one year old? I brought two tomato plants today but I put them in pots, my system is no way near being able to handle tomatoes as yet, I would stay away from any flowering fruit until your system has been running six months to a year?

But you don’t need to take my advice, as I am new to this too, I have just watched hundreds off you tube clips, my only experience is what I have learned off the net? But I am not doing to bad with the ideas I have put together for my system,

I wish you luck in your system,

A pH of 5.5 is at the very bottom end of most plants preferred range and definitely not a good area for your beneficial bacteria. For a wide variety of plants a more desirable pH range would be 5.8-6.3, but most commonly grown species of fish and the bacteria prefer the pH slightly alkaline, between 7.0-8.0. For this reason many AP'ers prefer to keep their pH between 6.5-7.0... a happy medium for the plants, fish and bacteria.

So when your pH eventually starts to drop you'd want to catch it in the mid-high 6's (it drops quickly once it gets below 7.0) and keep it there using an alternating combination of Potassium bicarbonate and Calcium hydroxide.

Don't worry about your potassium levels, or levels of most things you need to add really. You don't need to complicate things that much.

When I my system was new, I had tomatoes growing very nicely, with huge crops, and I was understocked, with no nitrite/nitrates showing up on my system. The systems will run off the smell of an oily rag.

All I added was seasol, and seasol powerfeed at times.

Grow whatever you like to eat. And follow Mr Damage's advice, worked like a charm for my high PH problems.

My tomatoes (and just about everything else) power along, running on only fish and their food. I used to occasionally supplement with Seasol, but ran out at the beginning of the year and haven't bought any more!

I reckon a lot of people see nutrient deficiencies because they over-filter the water and remove all the goodness which normally is released when the wastes are mineralised in the GBs.

Use quality feed. Stock at the right density. Feed at the right rate. Don't filter. Watch the system go.

re: pH whilst cycling. Nature has been doing this for a lot longer than all of us combined. Don't interfere with the process and let nature get on with it. As the system cycles, the pH will fall (nitrification is an acidic reaction). After the cycling is complete, if the pH is not in the required range, then adjust it, slowly. (Spectate, don't participate! Unless absolutely needed.)

I have expanded my growbeds out of the sump so I can directly see the difference between non-filtered and filtered - at this stage I'm having iron issues with the non-filtered beds


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I had the same iron issues continually when I was filtering as well. It's far less often now I've pulled my filters out.

Colum I'm having the opposite - the beds that are acting as the filters have a lot of trout poo in them and there is some brassicas that aren't faring well with iron. Where as the new beds that are running of the sump water have silverbeet and asian greens and no sign of iron deficiency - might be related to; the different types of plants, the flow rate, the greenhouse vs non greenhouse...