pH Controller Thoughts?

[Funkmotor]

So I've got my tank running and everything's growing and the fish and shrimp I've got in there look to be doing just fine.  But I've noticed that overnight - when the CO₂ is off - the pH in the tank goes to about 7.5 (in that area) where during the day it's closer to where I want it to be in the mid to high 6's.  (Just slightly acidic.)

All the standard tests are good (0 NH₄, 0 NO₂ and just detectable NO₃) but I haven't run a hardness test as I don't have one (it's on the list.)

Up to now I've been using Ottawa tap water (I'm in Nepean) which seems fine to me, but I've got the RO/DI set back up now to make top-off water.

So this sets me to thinking.  My pH could be getting pushed up overnight by those lovely rocks I've got in there (as they are definitely the kind that will do that), but then I'm torn because I do very much like the rocks.

And then I thought about a pH controller.  Instead of dosing CO₂ just when the lights were on, I could set the thing up to just maintain a set pH at all times.  I'd be using some at night, I suppose, but where it would cut in and out as needed I'd perhaps use less over time.  And I also wouldn't have to worry about a CO₂ dump killing my tank.

So...would that be good?  I've been out of freshwater for so long I'm not sure if there's a better way these days.

And, besides that, any suggestions or thoughts on good/bad pH ontrollers, or even controller systems that would do a good job of this and not cost a fortune?

[exv152]

PH controllers are a good thing, they save the lives of fish, they can avoid end of tank dumps for CO2 and they optimize the amount of CO2 used compared to someone who's running CO2 8/hrs a day non-stop.  But is it necessary, not really. I would be more inclined to use a pH controller to avoid pH dipping too low, say below 5.5, but I guess you can also use one the other way to reduce pH when it gets too high, but it'll costs you a ton of CO2 in the long run. As for the pH swings in your tank, I wouldn't worry about it. You can remove the rocks if you think they're contributing to buffering overnight, but even a swing of 6.8 – 7.5 is not at all harmful to the fish.

[charlie]

Just to add a few things , Eric is right when he says it`s good but not necessary, from my personal experience i did not use PH controllers for a long time mainly for 3 reasons i found them expensive , not reliable & not necessary.
As time went on i revisited the idea & with the help of Ray`s aquatic he suggested this new kid on the block - the now popular Reefkeeper, so i decided to try one - the reefkeeper lite plus, the selling points for me was with the plus i got 2 power bars , PH module temp controller & PH controller, this afforded me to get rid of the multiple timers for light & UV filter ( I only run it at night), a insurance  from my heater acting up & frying my tank & the PH controller which kept the PH on a more lever plain during the photoperiod.
The trick with the PH controller is finding the balance where your controll of co2 injection via PH, is a good balance with co2 saturation & harmless PH level. AT night the controller seldom allows the injection of CO2 mainly because your PH levels naturally rises from the reverse cycle of your plants - during light period your plants take in carbon @ night your plants give off carbon- so the chances of your pH rising enough to allow CO2 injection is vastly decreased.
The other thing as with any PH probe is to keep on top with your calibration
Regards

[Funkmotor]

Well, to prevent the tank dump perhaps that metering valve I ordered (yep, the eBay one) will help with that once I get it fitted to a regulator.

And so if there's really not much to worry about with that much pH movement, then I'll probably save my pennies for an actual controller that can do more for me than just regulate pH.

[daworldisblack]

The alternative perhaps is to have constant co2 diffusion. A very low bubble count - perhaps that would prevent big pH swings. The pH swings will probably affect your shrimps more if not just as much as your other livestock as they tend to be more sensitive. If your lighting isn't too strong, you could get away with constant low co2 diffusion and your livestock should be good as well so long as you're not overstocked.

[fischkopp]

I find controllers useful to record tank parameter. I usually look at the last 24h when I have my morning coffee and can see right away if something isn't working properly. It also helps a lot to preserve CO2 during the day as it will turn it off when it reaches the desired saturation. Nice gadget I find, but surely not essential. Changes of pH during day and night are completely normal and happen in nature as well.

About hardness: Nepean water is soft, very soft actually (KH =2, GH = 4). The pH tends to settle at 6.8 in my tanks with low bioload and minimal plants. So if your pH settles above 7 I would guess that something will increase the hardness; not necessarily the rocks, it could also be the substrate since you started with brand new. But that's not a bad thing, the opposite actually. I have to supplement KH/GH in some my tanks to create enough buffer and supply sufficient calcium/magnesium for proper plant growth.

[wrm130]

Speaking of supplement, when I tried diy C02 I didnt like the swing either...I ended up using aragonite in my filter to gently raise/maintain the kh.  This meant I had a higher ph but I was happy the ph didnt move around as much.

*still a newb but it worked for me!