Backyard Aquaponics
A place to discuss aquaponics

Hello,

Will this solution be ok to use in aquaponic system?

Neither are really used in Aquaponics.

This pH Down will most likely be Phosphoric acid, which isn't really desirable in Aquaponics, as too much could lead to algal blooms.

Plus, depending on what the starting pH of a new system is, in most situations you are best leaving it alone and allowing it to drop naturally on it's own over time, which it will.

If it is over about 8.2 when starting out, you could use a little Hydrochloric acid (Muriatic) to drop the pH to just below 8.0, then leave it to drop naturally on it's own over time. The beneficial bacteria prefer a slightly alkaline environment, as do most fish. The Chloride in Hydrochloric acid is also beneficial to fish health.

The pH up in this set will most likely be Potassium hydroxide, again, not desirable in Aquaponics, because when the pH starts dropping in an aquaponic system, it's because the carbonates in the water are being consumed by naturally occurring acids, so you want a product that will both raise AND buffer pH. Potassium hydroxide will only raise the pH, but won't add buffering capacity, which basically means you'll have to add much more and far more frequently.

As far as raising pH is concerned, you shouldn't have to do that for some time with a new system, probably months. When the pH starts dropping naturally, catch it and maintain in the high 7's using products that are also beneficial to the plants, such as Calcium carbonate, Calcium Magnesium carbonate, Potassium bicarbonote, etc.

I'd shoot lower than that. probably 6.8 to 7.2 if you're trying to optimize plant growth (usually best for vegetables in the pH 6 to 7 range). Most fish will do their best in the pH 6.5 to 8.5 range (breeding range) (they can go lower and higher though). The bacteria like a higher pH for nitrification (7.5 to 8.0) but will do conversion well enough down to about pH 6.

So I guess what do I use for ph up and down for aquaponics

Hydrochloric acid (aka muriatic acid) for pH down. Eventually you'll be adjusting the pH up. There are a lot of options for adjusting the pH up - carbonates, bicarbonates and hydroxides.

Examples of things you could use for adjusting the pH up -
Shell grit or coral or some other source of CaCO3
Potassium Carbonate or Potassium Bicarbonate
Potassium Hydroxide or Calcium Hydroxide - These don't provide any help with buffering the pH up but they can be used to raise the pH.

I use a combination of crushed coral and Potassium bicarbonate to raise the pH. I keep the coral in a mesh bag so that I can put it in or take it out depending on how the pH is doing. Usually the pH keeps going down very slowly even with the coral in the system and at some point I'll add potassium bicarbonate to bring the pH back up and supply some potassium.

Every system is a bit different in terms of how much to use and you only want to adjust the system water in 0.3 or 0.4 pH units at a time to avoid stressing the fish. Try adjusting a known volume of system water and see how much it takes. It's a good idea to let the adjusted sample sit for a couple of hours because the pH may drift and you may need to adjust it a second time. The ratio of the amount used to adjust the sample to the sample volume should equal the ratio of the amount needed to adjust the system to the system volume. This will allow you to calculate the amount needed for the whole system. Hope this makes sense

Good spot Scotty, Cheers!... A typo there locchamp, that should've been high 6's, not high 7's. Too many things on mind, typing too quickly.

thanks all

I should mention that with the crushed coral I adjust the system directly by just putting the mesh bag under a grow bed spigot. Most CaCO3 sources could probably be used this way because the pH changes they cause are relatively slow.

Cheers Mr Damage

Surely if the PH is low (like low 6s - high 5s),the crushed coral will dissolve quicker?

Yes, that's true but keep in mind that you're fighting the effects of nitrification too. In my case it's sometimes not dissolving enough to counter the nitrification and that's why the pH keeps dropping - you need the addition of something like potassium bicarbonate that dissolves easier. You do have to watch the pH and remove the mesh bag occasionally (especially if your not feeding much) but it takes long enough to change the pH that I am not concerned especially since this would probably max out at a pH of 8.2 (I've never had it get this high though). Using something with potassium is also a plus. Hope this makes sense to you.

Thanks