Backyard Aquaponics
A place to discuss aquaponics

I agree that the CaCO3 will remain in the system and disolve as needed. I am not certain though that it will not get any higher than 5dKH. I want to add some more to the system anyway - bacause I have less in there than I would like so that I have plenty in reserve - so rather than doing the test in a glass I will do it in the system. Time will tell whether 5dKH is the mark at which the KH stays.

Cool. Let us know. The logic behind my theory is that its not going to show up as hardness unless it dissolves.

I have not read Earthbound's book Herecy

Why is everyone trying to hold high pH (7.2-7.5)?

Most Plants like 6.5 more. And lower pH allows more ammonia tolerance. Is it the fish that want an alkaline environment?

I was planning on stabilizing at 6.5. What kind of problems does that cause? My well water is about 7.8, so it takes effort for me to do 6.5 unless I find the bacteria bring it there (my system is not cycled yet, so I do not know where it would stabilize on its own).

I guess this is hijacking VB ....should I pose this question elsewhere??
This is an important issue for me.

isn't it the bacteria that prefer the higher pH?

Doug,

Nitrifing bacteria is less efficient at 6.5, especially the one that converts the nitrite (nitrosomonas i thnk).

You can definatly do 6.5, but at ph 6 pretty much all nitrification stops.

7.2 seems the be where Calcium carbonate buffers the water too. Its a great buffer for us becasue;

1) contains calcium not sodium

2) can be free (egg shells or sea shells)

3) isn't very soluble, so ph change is slow (up to 7.2ish)

Make sure you understand the term BUFFER.

The nitrogen cycle naturally makes PH drift lower so if you are at ph 6.5 and unbuffered, you quite easily drop to 6 and below. I'm unaware of any PH 6.5 buffers applicable to us(let me know if you find any).

Home this makes sense.

Steve

As Steve said - the main point is that CaCO3 buffers to PH to 7.2. Once you are at 6.5 you are on your way down and it is going to be hard to keep it at that rather than drift down to 6 and below.

EB mentionned the other day that his system is about 6 and is coping - but not all systems are as big as his or as mature - so may they may not process the ammonia/nitrite sufficiently.

Thanks VB

An update:

System is stable. I am getting ammonia and nitrite readings following daily feeds - but they are low and safe levels. The bacteria are clearing it out of the system in good time.

I am pretty sure the nitrate level has dropped a little (though it is always hard when it is in the 80 - 160 range). If so - this is good and it means my plants are starting to have a better impact.

PH is still 7.2 - though I note that dKH has dropped from 5 to 4. I will add more CaCO3 on the weekend and monitor its effect on dKH.

Plants are looking pretty good - the Paw Paw is getting pretty big (close to a metre tall now). I know I am going to regret not getting it out of this grow bed (as originally intended).

Am at a course this week and had to say what my passions are in my introduction. When I advised that permaculture and food security were interests of mine and that I was growing fish in my backyard - I could just see everyones ears prick up. I decided not to have a rant about peak oil . I have found in my travels that there are more and more people around who are getting back to the simple pleasures of growing their own fruit and vegetables. Very pleasing :-).

Doug-B

My system sits at 6.4 tp 6.8 without any intervention. I am always amazed how stable the ph is once the system has settled down.

Muzza

Heh Murray - you have been fortunate. My system PH stayed quite high until a few weeks ago. The nitrification process pulls PH down - so unless the system is well buffered then the PH will naturally drop.

A lot of people of course buffer their systems with shell grit or, in my case (since PH became an issue for me), calcium carbonate in the powder form.

Some water supplies will have some carbonates in them already due to their source. Because you get your water from rainfall Murray - I would not expect the water to be buffered at all. To confirm a KH test could be performed (it would almost defintely read as 0 straight from the rainwater tank.

My theory (untested) as to why your system PH has not dropped lower at this stage and why mine took a good six months to drop to danger territory is that there may be some carbonates in the gravel we use (again I stress that I may be entirely wrong here).

Can you confirm Murray that you have not put shell grit or any other known carbonate source into your system. You do have carbon in there don't you - Steve would this carbon be a source of carbonate???

The main point I am making is that unless the water in the system is bufferred in some way (either naturally or artificially) - then there is nothing surer than the fact that the PH will end up dropping to 6 and below due to the nitrification process.

Hi Murry just a quick one are you still runing coco or what ever and has the system cleared

nah, carbon aint gonna do nothing.

it might be the media

heavy feeding rates will always bring the PH down faster too.

A measure of the KH would be in good order muz

As discussed in another thread over the last couple of days - Murray's water has been buffered due to rock dust addition.

If you believe all what you read (I mean the blurb on the company's website), we should all have that stuff in our systems.

Les came over yesterday to drop of my share of the 32mm pressure pipe we bought off ebay. My share is about 200 metres .

While here, I wanted Les to have a look at my fish to give an opinion on their size. Unfortunatelly they can be quit hard to spot against the algae coverred background of the fish tank as they hid in the shadows. They are definitely getting quite large though and I think Les' opinion was that they are significantly larger than what I have been quoting. I expect the biggest ones are pushing 500 grams (would definitely be no smaller than 400 grams).

As usual - was good to have a fellow aquaponics enthusiast here to speak crap about AP