Backyard Aquaponics
A place to discuss aquaponics

Thanks again all, I have 35 trout and 15 silver perch and today got up to 37C and water up to 24C. I always have 400L of water on standby from the tap and gassed off with an air stone for up to a wasp any water added should be good so I wonder why my pH is dropping as it’s pH 8 from the tap. When the rhubarb takes off it’s a sign of lower than pH 6.5 so the question is the best way to raise the pH. I have shell grit in the system and lime etc but all the labels have rubbed off and so no way of knowing how much to add to the system. FT is 2500L ST is 900 L RFF is 190L MBBR is 100L plus 3 large growbeds approx 1200L all up.


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Even with the labels you wouldn't really know how much to add - in order to know you'd have to test out your water and see. Take a known volume of your water into a bucket and add a known amount of the chemical you are using to adjust the pH. Keep doing this until you get the pH you want. Once you have this ratio of amount of chemical needed (to raise the pH of the water) and the volume in the bucket you'll be able to up the amount of chemical for the volume of water in the system - the ratios should be the same.

I still prefer to make the adjustment using the removal and re-addition of water from the system to get a more gradual change. This causes less shock to the system and is much easier on the fish. The changes should be 0.4 pH units or less per change to keep stress on the fish to a minimum. It will be difficult to know what change you're doing initially since you really can't be certain of the system pH at the moment. In case you mess up though, most fish will survive much greater pH changes.

Considering that you've used different forms of calcium carbonate so far, I'd change it up every once in awhile and use Potassium bicarbonate to add some potassium back into the system and raise the pH. I use both calcium carbonate and potassium bicarbonate. The calcium carbonate only slows the pH drop for my system. I use the potassium bicarbonate when the pH has gone down more than I want and I need to bring it back up (it also adds buffering capacity). Some people use hydroxides. Usually they'll alternate between sodium hydroxide and potassium hydroxide - these are much more potent so you have to be extra careful when using them (they don't add buffering capacity either).

Re the water from the tap - Sometimes the pH of water out of the tap changes as it's exposed to the air. Try giving the water time to reach equilibrium and see what you get for pH.

You must have had a few warm days to be at 24C Liney. So far over here we have only had the one hot day, but a couple more due this week.

I reckon I have read a few people who do trout add regular amounts of lime etc to try and control their pH. i.e a set amount each week based on the amount of food the fish are eating. May help in the future if you have someone else running your system while you are away.

Cheers Brian, my water temp is an aquatic thermometer dangling in the FT so doesn’t get to the bottom which is 2M deep and I have a massive air diffuser pumping the O2. I went and got some pH up and am adding 50ml at a time to see where I’m at. I do have line etc that Mr Damage got for me but will have to try and get him over for a personal consultation to maintain my systems balance.


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Added the pH up but not great results. At first after 4 hours it looked to be around 8 then bottomed out below 6. And my bacteria colony has all but gone as the Ammonia is at 4 ish. Absolutely pi$$ed as I had a feeling this could happen while I was away. Hope the bacteria grows fast as the weather is warm and wet.


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Hiya Liney, not sure why Damage sold you pH up, many other cheaper options as Scotty mentions in the above post. Definitely good to have a top up water tank to set the pH in the water before adding it. Me, I just use a cup full of lime or potassium carbonate into the gb feed pipe. Perch can be tough buggers.

I got the pH up from bunnings as it’s close by. I have some potassium bicarbonate but not sure how much to add to the system.


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I also have 400L of back up water from the tap as I mentioned that sits there until I need it and is pH 8 and I add it regularly but never does anything to the overall systems pH which is frustrating. I’m more concerned with no bacteria to process the ammonia.


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Exposing the fish to pH 8 with ammonia in the system could potentially harm them, and will at the very least stress them, even if the pH bounces back fairly quickly, which is why scotty and brian reccomend adjusting the pH in a seperate tank before re-introducing it to the system. You should remove some system water, raise its pH, this will take time and maybe more than one addition of base as the pH will bounce back towards its original figure but remain a bit higher each time. Once the pH has stabilised you can return the adjusted water to the system.



That's the way pH works; you can't tell how much a given volume of water will change the pH of another volume of water just by its pH, it depends on the water's hardness/alkalinity, the amount of carbonates etc. That's what the term "buffer" refers to. When water is hard it is well buffered against acidification, its pH is more "stubborn". You can have water with high pH, but without much hardness, which will not be effective at shifting the pH of another volume of water. Perhaps this is the case with your tap water.



So is the shell grit permanently in the system water? It should be as this should help buffer the system water against the dropping pH. If it is in the water then it doesn't seem to have worked, perhaps it has been consumed or is in a place with poor circulation?


The amount of potassium bicarb, lime etc you will need is a matter of trial and error until you have an adjusted volume of water, then you calculate how much this will effect your system pH according to the volume, ie, if I remove half the system water and raise it by 1 pH and then return it I will raise the pH of the whole system by 0.5.

Its just a thought and may not be practical, but if you had an extra pump maybe you could isolate the sump and 1 growbed and treat the water in the sump, then when its stabilised and the bacteria are back up and running you can do partial exchanges with the fish tank water and also with the growbed media to try and kis¡ckstart the other growbed back ito action.

Cheers Danny I really appreciate everyone’s help in this. I have the shell grit in a bunched up shade cloth next to the GB returns but maybe add some more and not bunch it up too tight?
I also brought a water filter used for caravans to remove some chlorine etc and noticed the pH was near 7 compared with pH straight from tap.


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I reckon that would be a good idea. I'd probably just sprinkle and mix it throughout the media in the growbeds. A small quantity of it directly at the growbed inlet etc so that it can be observed would be a good idea, as it will eventually be consumed, indicating that more should be added.



I think these filters intended for drinking water remove some calcium and general hardness from the water, which is why it ends up with a lower pH. That might be all well and good for drinking water but for AP we want that hardness to buffer against acidification.

I reckon that would be a good idea. I'd probably just sprinkle and mix it throughout the media in the growbeds. A small quantity of it directly at the growbed inlet etc so that it can be observed would be a good idea, as it will eventually be consumed, indicating that more should be added.



I think these filters intended for drinking water remove some calcium and general hardness from the water, which is why it ends up with a lower pH. That might be all well and good for drinking water but for AP we want that hardness to buffer against acidification.

So the concrete has been finished and the system is back online with the addition of another 500L GB and a purpose built shade house over the majority of the system. Having a few issues with flow into the RFF and the MBBR as I’ve now plumbed the extra GB into the MBBR. Unfortunately if I increase the pump flow to the FT it doesn’t increase the flow out of the 2 inch SLO which is a pain in the butt. I need a little more flow rate to enable the new GB to break siphon.
Here are some new pics



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Hi!,

AAARGH! Those pictures are HUGE!

Just uploaded them off my phone through the Tapatalk app- a lot easier than trying to find them on my computer.


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