Backyard Aquaponics
A place to discuss aquaponics

I want to make sure everyone knows that the pH of your tap water immediately after you draw it from the pipes, may not be real pH of your tap water.

This is some info that I didn't originally know it is caused me all sorts of confusion. Water from the pipes or well is often depleted of O2 and full of CO2 the carbon dioxide in the water forms a weak acid which will give a lower pH to the water if measured right away. If you take that same water and let it air (run it through a system or put it in a bucket with a bubbler) to let the CO2 escape then test the pH again, the pH will often be much higher. Example, my well water comes out of the tap with a pH of about 7 usually and after outgasing, it will have a pH of about 8.

This is important to know when doing water changes in a system that is likely to settle with a much lower pH or if dealing with a system that is not fully cycled and you are having high ammonia since higher pH makes ammonia more dangerous to your fish.

It is also good to know this info about tap water when dealing with pH balancing issues. If you are trying to hold a pH around 7 and adding lots of tap water causes pH to go up, then you want to keep water changes and additions small so the system can bring the pH into line without lots of bouncing.

(moderators, I think this tidbit might be worth a sticky, Thanks)

nice one TC.

Sort of the same conclusion we came to for Tony from west oz (i think) with his bore water

I had the worst time trying to deal with my Hydroponics before I learned this little bit of information. I just couldn't understand why my hydroponic system pH kept climbing since he nutrient mix usually dropped the pH of water down into the 6.4 area and my tap water tested as 7 (before I knew to air it before testing) Why the heck would the pH keep rising above 7 dang it.

Now I know but had I not known this, I could likely have caused some fish deaths by bouncing the pH more than would be wise.

this will be why my PH was around 8 when I tested on Tuesday...
I adjusted and added tap water at the same time... took a reading, adjusted a little more... got just over 7 and left it... next day the PH was higher!!! though that the ph meter was on the fritz!
Feel better now

I've got a half barrel that I fill from the tap and let it sit before I use it for water changes. Might make one for the garden as well. Can't be good watering with the chlorine.

I used to do the same... but when my water mass rose above 3000L I just topped up straight from the tap... Guess I got lazy!

heh, once I was over 20l it was straight from the tap

Even the aquarium gets tap water, just have to do it slowly.

Materials in the system can also buffer the pH up or down. My growbed gravel is limestone and my tap water is from a limestone aquifer. These two are keeping my pH above 7.6 and veggies just refuse to grow. I'll be changing these out soon to other media and rainwater. 'Course I'll slowly mix (over weeks) in the rainwater with the current water to prevent drastic pH changes at once. And slowly change the gravel also to give the bacteria a chance to transfer to the new media quicker, maybe mix the two for a week or so.

Great info. Thanks. Just finished my first aeroponic build, and have been studying aquaponics for about a year, gonna take the leap soon =D Really looking forward to taking advantage of this information. Cheers.

I need to knock 2000 liters of 8.5 ph water down any tricks

HCL

Great info TC, never knew

I run only rain water in a rain water tank so i think i may be a little safer than some - i think?

Rain water will tend to be a bit acidic so you should be careful about the materials your catch rain water with and store rain water in. If you are collecting off of galvanized roofing or other metals, the acidic water will leach metals from the roofing material that can build up to unsafe levels for fish, also if storing the water in galvanized metal tanks the Zinc levels could be too elevated to be safe for fish.

If storing the rain water in unsealed concrete tanks, the concrete will probably leach enough calcium carbonate to buffer the rain water to a point.

Take these factors into account when trying to understand what is going on with your water.

Rain water is great in my opinion but you do have to understand that pure rain water doesn't come with much in the way of minerals of buffering capacity so you may need to keep a more careful eye on your pH and use more materials to help buffer and stabilize the water. Fish need some hardness and minerals in the water as do the bacteria.

Here in Houston I am finding I always have HIGH pH, 9ish regular out of the tap.

I posted this on another thread but did not get any response so thought you might have some idea about this problem?

I have had a 1200 gal pond in my back yard for 3 years. I have been reading all I can in the last month or so re. fish, aquaculture, aquaponics and the associated reading. I have raised Koi (4" got to 24") and goldfish for years.

Have never had a problem, other than when my mother came by when I was on vacation, she saw the pond was about an inch low so she added some hose water, she forgot and went home! All my 2 year old fish including 3 24" Koi dead! Oh well, things happen.

,So cleaned pond well, filled with water waited a few weeks and put 15 goldfish and 15 Rainbow Dace in. All lived great not one lost fish. That was about a year ago.

pH has always been high around 9, fish guy at pond store said should be fine, and it was and has been for years.

In an effort to get good at AP and get some practice in raising vegetables with fish I have seen that some of the nutrients might get "locked out" at this high pH. So I purchased some Acid Buffer. I made a 5 gal bucket of around 5 pH and created a wicking effect to slowly wick the 5pH water into my pond. It was working great but very slow, I got antsy and put about a qt in last night. Pond water went to just over 8pH and I thought that was fine. But today I found 1 of the small Rainbow Dace dead, 1st fish ever (I don't count the 3 pacostomus (sp) didn't know they couldn't take 45 deg water, oops)

So it's obviously the fast drop in pH, what do y'all think I should do? How is the best way to buffer slowly in my system my tap water is in the 9 range. So every time I do a 20% water change which is once a month my pH will jump up.

Thanks for any help, and this site is GREAT! LOTS of great info!!

Rob C

Treat your top up tap water with acid to about pH 6...... over 5 months you should have basically exhausted the original carbonate hardness...

And along with nitrification... the pH should fall below 7..... when it falls to pH 6... then buffer it baqck with some "untreated" top up water...

Patience... is the key...