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What would you add to get a potassium boost for your plants ?

How and what do you use to lower ph in a just starting up aquaponic system ?

Can you foliar feed organic things like seaweed , bat guano , molasses compost teas if you get on the plant leaves and very little into your recurculating water ?

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First up, what do you want to get blooming?  I have never added anything extra during bloom / fruiting periods as you would in hydro, but I know other people do add foliar sprays for extra potassium / micro nutrients to good effect.  If I recall correctly, one of the options was foliar spray of potassium bicarb, which doubles as a fungicide.  If you search "potassium bicarbonate" and "foliar spray" in the forum section you may find the discussion threads.

seaweed extract like Maxicrop or seasol are common ways to get potassium and they can be foliar fed as well as adding some to the system.

 

Potassium bicarb is a good one for keeping pH up.

 

Lowering pH is more of an issue since you need to figure out why your pH is high before you will know if lowering it is really an option.  muratic acid (hydrochloric acid) is an option as are many other acids but you probably want to avoid having to constantly add anything to your system to lower pH.  Switching to rain water or RO water for topping up.

 

A high pH (up to say 8.2) at the start is usually not a big problem as it will come down on it's own eventually but if you are constantly topping up with a lot of really hard water then you may have issues.

the PH of my tap water is 8.8 to start with is that going to be a problem?

 

Jane, I will try to get that down closer to the neutral range.  That high a pH can stress many organisms, and is likely to lock out or reduce availability of many nutrients (particularly iron) to the plants. Your ammonia and unionised ammonia toxicity at such high pH is also extreme.  At a temperature of around 25 degrees Celcius (what is that - about 77 F) you are looking at unionized ammonia at 1.77%, but at your pH of 8.8 if will ramp up to between 15 and 36%. It is the unionized ammonia that kills fish quickly (NH3 as opposed to NH3+N / NH4 depending on how you are accustomed to write it).

With really high pH tap water you might want to look into using rain water or RO water.  To figure out how necessary that might be you might want to run some experiments with a bucket or barrel of your tap water and some acid.  You want to see how much buffer is in that 8.8 water to see how much of a problem it will really be.  If it is simply alkali but a single small dose of acid will bring the pH down AND keep it down then there isn't too much buffer there and you might be able to cope with it just using a little acid to adjust your top up water before using it in a system.

 

However, more likely is you will add acid to the water and the pH will come down but the next day when you check the pH will be back up and it will take many doses to use up the buffer therefore liberating too much calcium into the water which might also cause you issues with potassium in the future.  This is kinda the case with my well water so I've taken to collecting rain water for most of my system top up purposes at least in my two smaller systems.  With the rain water I actually need to add buffers to my system to keep the pH from dropping too low so I can alternate between potassium bicarbonate and calcium carbonate to also keep the potassium and calcium levels good.

So with my bucket of water that I test , can I use just PH up from the hydro store or what other acid and from where?
I'm not going to comment on where to get supplies in the US, but there are a number of threads here about pH balancing in aquaponics.  People use potassium or calcium hydroxide, potassium or calcium carb/bicarb to lift pH, and a whole lot of different acids to lower - I use nitric or formic acid, but I do not see many other people doing that. Take a look at the pH threads and decide!

Yes there are many pH threads.

 

Beware of Hydroponic pH adjusters and check the ingredients before using them.  Some are just fine like phosphoric acid but others have lots of ingredients including ammonia and can cause a terrible ammonia spike which is bad for fish if they are already in the system.

 

I've used pool acid before (sulfuric acid) but that isn't something you really want to be using huge amounts of regularly.

Others have used muratic acid (hydrochloric acid) which can be found at Ace Hardware in my area.

 

I don't really recommend adding acid directly to an AP system and I wouldn't recommend using it all the time.  If your source water is so hard that you need to use acid all the time you may be better off collecting rain or using an RO filter or something or even a water softener as long as it doesn't add too much salt to the water.

 

If your media is causing the high pH, don't bother with acid as it won't work and will cause more problems than it can possibly fix.

 

Vinegar might work in a pinch but it breaks down and isn't long lasting.  (It may also have some antibacterial properties that are not desirable when cycling a system.)

 

I don't recommend citric acid since the antibacterial action of it is stronger and can really inhibit bacterial cycling.

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