Backyard Aquaponics
A place to discuss aquaponics

So I've been doing a lot of reading lately, and in particular, I just finished reading TCLynx's system thread and I've been thinking a lot about pH. With TCLynx's system I've been noting the things that did and didn't grow well for her seem to follow right along the lines of her (for plants anyway) high system pH. I've also noted her comments that if she had it to do over, she'd hold off on the shells and use them as needed.

From there I went off and started looking up suitable pH ranges for the various plants I wanted to grow as well as the fish I had in mind.

Most plants (that I'm interested in growing) seem to have a max pH range of around 7.0. Some a little higher, a few others top out around 6.5.

On the fish (Channel Catfish, Rainbow Trout, Brown Trout) it seems the tolerable pH depends a lot on the water conditions as well which, not having built anything yet, I'm rather uncertain of. The lower range for them seems to be around 6.4-6.8 depending on what report I read, but I suspect that with "perfect* conditions (which probably don't exist) they may be good as low as 6.0.

So I have several questions:

1. Anyone safely run a system down in the 6.0-6.5 range? How much is that "flirting with danger"?
2. Anyone aware of freshwater fish that are perfectly happy at 6.0?
3. It's my understanding that an unbuffered system generally sees the pH drop over time, right?
4. Assuming #3 is true, how well would it work to have a system where the growbeds drain (gravity) into a sump, I pump water off the bottom of the sump to the fishtank, and I control the pH of the system by adjusting the amount of shell I put in the sump? (so the water has to run through the shell to get from bed to tank) Can I maintain steady pH levels around 6.5 doing this?

Gblack.. I consistantly run all my systems between 6.4 - 6.8... as do many others..

I've had my systems down as low as 6.0, and others have gone to 5.8.... however I do not advocate running levels below 6.4 for any extended period...

This however does depend on the actual fish species, but in general (IMO) freshwater fish, which by nature either have very small scales or more generally employ a slime coat for protection.... and as such have some ability to counter pH levels that are more acidic by producing more slime coat....

This can be promoted by the addition, and maintenance of salinity in the tank... and I run 1-2ppt as a matter of course...

Below ph 6.4 requires the addition of a buffer, either periodically or constantly by utilising shell-grit... and most people do so as a practise... as you suggested by either placing the shell-grit under the return to the sump or inflow to the growbeds...

Systems that tend by nature to begin with pH between 7.0 - 7.4... will drift over time, but the addition of shellgrit tends to hold such systems around 7.4.... and is self regulating...


Systems that start around 7.0 howver acidify much quicker IMO... and while shell-grit may buffer back for a period, never seem to hold the same sort of self-regulation and exhaust the buffering capacity fairly quickly with pH dropping back to 6.4 - 6.8

From my days of hydroponics, this is the optimum pH range for nutrient uptake by plants... and IMO is tolerable without great detrement to MOST fish....

Catfish and some other species may be more prone to stress and fataliies if exposeed to pH below this however...

As a general (unsubstantitated) rule... I believe that any species that by nature has a particularly heavy slime coat... i.e catfish... may not tolerate pH much below 6.4 for extended periods...

A few notes about my system and conclusions I'm beginning to draw about why I've had trouble with certain plants. My true problem may not be as pH related as it is mineral related. There are others out there with systems that run at a pH of 7.6 like mine who have had no trouble whatsoever growing things like cucumbers. OBO has lots of shells in his system and a steady pH of 7.6, however he has lots of iron buried in his grow beds and perhaps his source water has more iron in it and he added lots of seasol during the first year of operation and cucumbers grow fine for him. I don't think my well water has much if any iron in it, great for my plumbing fittings in the house but a pain for the AP system since it mean I need to add lots of iron. I think if I was to supplement heavily on the potassium and iron at the right point in the life cycle of a cucumber plant in my AP system, it would grow fine. I have had some small success with this.

Anyway, back to pH. You might want to do some research into your source water before you decide what you will be doing for the AP system. Why I say this, my well water comes out of the ground with a pH around 8 much of the year. If I were to set up a system that tended to a pH of 6.5 and then have to do a lot of topping up or water changing, then I would be bouncing the pH quite a bit when ever I added well water. I am probably kinda lucky that I'm buffered so well since I don't tend to monitor the pH as I add water to the system. A few tips about researching your water, tap water is usually full of CO2 as it comes out of the tap so you should aerate it or at least let it sit out overnight before testing it's pH or you will get a false low reading since CO2 dissolved in water is a weak acid (if I test the pH of my water right out of the tap, it will usually read 7 but if allowed to aerate a bit, it will usually read around 8.)

pH 7.4-7.6 is what you can probably expect from a system buffered by lots of shell/shell-grit...

And yep TCL... iron and potassium are probably the two most important elements that would need to be supplemented at that pH.... at the appropriate times in plant growth...

The regular addition of Seasol/Maxicrop... which are high in trace elements in solution... and particularly by foliar spraying helps enormously...

I also regularly top my systems with pure, clean straight sea water... sea water is very high in trace elements and minerals...

I suppose my main point here is that all other things being equal, plants are actually able to accept a far wider range of pH that we usually give them credit for as long as all the elements they need are present. Heck, if you followed the pH recommendations of Hydroponics as law, most Aquaponics systems in operation are doing the impossible

So, see what source water you will be working with before deciding things too specifically. Keep in mind ongoing maintenance, if you set up a system that needs regular or constant buffering attention to keep the pH from falling into dangerous ranges then be ready for that. If you go with the heavily buffered system method then the fish and bacteria will be fine but it might take a little more effort to keep all the plants happy by supplementing the potassium, Iron and trace elements (which even in the low pH system, those supplements are generally needed too.)

Dont forget the main reason to stay above a pH of 6 is the bacteria.

Depending on temperature, if the pH goes below 6 for any extended length of time, you will have a massive die off of bacteria. leading to a huuge ammonia and nitrite spike. Bye bye fishies.

This process has been seen in quite a few systems now. You may get away with 5.8 for a while, but it may go to 5.75 for whatever reason and snap kill the bacteria. It appears to be a very rapid process.

Thanks, I missed the bit about the bacteria. Given that I always like to leave myself some leeway instead of living dangerously, that means I need to stay away from the 6 end regardless. I do think I would like to run a system lower than 7.0 though. Even if it may be possible to make things work above that, I figure the more positives I've got the more likely I am to cover myself in the event of the inevitable screwup of some type.

I've been watching the various comments on mineral deficiencies and I've been wondering how much of that I could possibly correct just by using some better fish food - like perhaps earthworms. However, I'm real uncertain about how much and how easily I can pull that off. I figure I'm going to have to use some of the store bought stuff one way or the other though. All reports I've ever read of it being tried indicate that many freshwater fish really go nuts over earthworms. There are probably some other good options as well if I could find easy ways to raise them. One of the concerns with earthworms will be finding a semi-painless way to harvest them.

One thing that's kind of struck me about fish diet was when I was fishing last year and caught a brown trout - wasn't real big, probably about a foot long or so, but big enough to eat. When I went to remove the hook from his mouth to my surprise he had about 3 earthworms, a pill bug (which was still alive believe it or not) and a bunch of other stuff running around in there - his mouth really wasn't that big either.

When we find something in AP that's missing and has to be added in such as Iron, that's just like a flashing neon sign to me that says "Hey, you're missing part of the cycle here somewhere, what can we change so this is included naturally?" After all, nature works

I've had concerns about salt in the water because I'm not certain how well some plants may deal with salt. I think peppers and tomatoes do well, but I'm not certain about other types. Anyone have some good info on this?

Rupert - do you have some better suggestions for fresh water fish? I'm looking for something that can tolerate some cold, though I do intend to do this in a heated greenhouse, so if things go as planned that's not strictly necessary. My biggest issue with fish selection is state laws. Tilipia are a no-no for me. Certain types of Bass are a possibility. Catfish tastes pretty good though (and I must confess, like others here have - I'm not a fish person when it comes to food. I'm in this for the plants. The fish are an added bonus.)

What's a good way to buffer a system in the 6.4 - 6.8 range (good meaning things are stable and maintenance is easy and infrequent)?

TCLynx - I've not said much, but I would like you to know I'm impressed with your system - but even more impressed with your general all around ingenuity. To run a system (or build a system) like that obviously takes a fair amount of work and effort, and then given your diligence observing it, you can rest assured I was paying attention when the question came up of "What would you do different?"if you had it to do again.

My source water will end up being from the tap. I believe I'm going to have secondary water available to me (basically pumped out of the lake or other similar places with some pressure added) but given how much effort all of you seem to put into quarantining new fish, I'm afraid to use it for fear of what might be in it. It's suppose to be safe for dirt gardening though. I'm uncertain what the pH is, but I do know that water softeners are real popular around here, so there may be hardness issues. (and I am aware I've got to divert the water BEFORE it hits the softener so I don't load my system down with salt).

Kind of in line with all of this - anyone have any good recommendations on monitoring/testing equipment? I have to admit that I'm not to keen on having to try reading a color chart. My order of preference for equipment would be along the lines of :

1. Digital, network connected equipment that can handle constant submersion
2. Other measurement device of some sort that can handle constant submersion and doesn't require a color chart.
3. Digital handheld instrument of some sort requiring no or infrequent calibration - or possibly some sort of frequent calibration that is simple, quick, and inexpensive in nature.
4. Other measurement device not requiring a color chart used periodically.

I'd also like advice on what things I should be measuring (in order of importance) so I can see if I've missed or under prioritized anything.

Thanks,

Gene

I don't think you could get away with feeding the fish more iron since metals are something that most creatures don't pass through their systems as well as other things like nitrogen and phosphorus. This is why supplemental iron often needs to be added unless the grow bed media has lots to give up to the plants. You might try loading your grow beds with a fair bit of green sand to see if that heads off the need to add iron and potassium though.


small amounts of salt (like 1-3 ppt) don't seem to give most plants much trouble. The most sensitive plants to salt that I know of seem to be strawberries and sweet potatoes. 3 ppt didn't seem to bother my strawberries through. My sweet potato vines have seemed to suffer a little when I salted above 3 ppt last summer. Most of my other plants didn't even seem to notice salt up to 5 ppt.


Catfish are probably a good choice then unless your water can stay cool enough to do something like trout. I don't know how difficult or easy bass may be in tank culture. Otherwise perhaps a koi enthusiast will pay you to grow out some of their stock for them?


There's the rub, most good automatic, self regulating buffer materials are gonna give you either a 7.4-7.6 range or limestone/marble is likely to buffer up around 8. To keep a system in the mid 6 range, you have to monitor it and add more shell grit or other buffer material as the old stuff dissolves or looses effectiveness. Some people actually have to add potassium bicarb or other material to the system on a daily or weekly basis. I don't know of any material that will automatically buffer to the range you desire without manual intervention and monitoring.


CHIFT PIST all the way. Definitely have the water go through grow beds before returning to the sump so that the pump can enjoy clean water. Makes keeping the pump clean and flowing so much easier. I'm actually thinking that using the shells in my system wasn't such a bad choice anyway.


Hard water is not a bad thing for Aquaponics but you should get yourself a pH test kit so you can research your water a bit.


The dropper and test tube kits are not as bad as you are fearing. Yes they are a bit tough to deal with at first but once you get used to them it really isn't bad at all. During initial cycling and when adding fish or after a major change etc, you will be doing lots of testing but once the system settles in, you only test occasionally.
The most important tests all come in a handy Freshwater master test kit and include
PH
PH high range
Ammonia
Nitrite
Nitrate
Those 5 are the really important ones especially through initial cycling and if you start having any problems. A good temp guage for the water is also a good idea.

Some other tests that people sometimes like to have include (but these are not mandatory or even recommended)
Dissolved Oxygen
Salt level (I've been using a hydroponic EC meter to estimate my salt levels)
Carbonate Hardness
Copper, Zinc, Iron or other metal tests (example of someone having fish die because of using galvanized tanks-zinc)
Phosphorus
etc I'm sure there are many tests that people might do but I doubt I'd spend a lot of money for too many extra tests/equipment.

I do not think you are going to find a single piece of equipment that can do all the tests you want that does not require calibration (and most calibration requires having the calibration liquids) and replacement probes and and and. How much are you wanting to spend on this equipment in order to avoid the color cards? How accurate and reliable do you expect such a meter to be? I've seen meters that can measure pH/Conductivity/Salinity for as little as $140 but then you need the calibration solutions and I'm not sure how much I would trust such a meter. (I've had cheap pH meters that no mater how much you calibrate them, they never really worked right.)

Now if you really can't deal with reading the color cards....... And you have the extra money to spend, there are systems that can read the colors for you. Now they still use test tubes and reagents that you have to deal with but then the meter will read the color and many can be hooked to a computer for logging the results. The meters themselves can cost between $700 and $2000 US and then each pack of reagents costs between $10 and $200 depending on the meter and type of test. The cheapest $795 ($995 if you want to hook it to a computer) unit I have seen plus the reagents to do the pH ($13 for 50 tests, instructions and accessories ), Ammonia ($41), Nitrite($19), and nitrate($47) So that is $1115 plus shipping for a meter that can do the same thing as a freshwater master test kit that costs between $18 and $40 depending on where you get it. Bonus of such a meter is there are many more reagent kits to allow for testing of many other elements. However such a meter is not going to be automatic or continual, you still have to do the tests. I can't find any single meter that can have a probe continually in the water that will test for all the things you need. The closest to that you might get would be a pH monitor that will also do temperature (still needs regular calibration.)

Good Luck with it.
Oh, most of the info about meters/tests and probes I got from
http://www.AquaticEco.com