Fluctuating PH with auto CO2 - Help!?!
Ok, so here is my situation. The main problem is that my PH is fluctuating by around .3 . Sorry if I am long winded. I have an automated CO2 set up with a Milwaukee controller. The set point is set for 6.5 and CO2 is pumping out like crazy (maybe 4-5 bubbles per second....I set it this way). My drop checker indicator has historically shown that I do not have enough CO2 dissolved in the water, but yesterday I had the ideal mix.
Now, based on the appearance of my tank and plants, everything looks great! I have a full carpet of glosso, a thick jungle of Bacopa and Lugwigia, medium swords, spreading hair grass, and a few others. Plus all the plants are bubbling off lots of oxygen! This is great huh!
Well, the reason for my concern is that on Tuesday I will be getting 6 half dollar sized discus from a local hobbyist breeder and adding them to my tank (yes, a planted tank is not a big enough challenge...I am going to up the ante and attempt to grow out discus in the planted tank!). So, as you might imagine, the fluctuations in Ph concern me...I don't want the fish to die. Currently, I have two flying foxes and a couple of ottos and they have been doing just fine (but they of course are not Discus!).
So, back to the PH fluctuations, my tank has an overflow and a homemade trickle filter. I imagine that I off gas a good bit of CO2, but I have raised the overflow pipe and sponge, added 3 sponge walls around the interior of the over flow to slow the "water fall" effect, I have covered both the over flow and trickle filter with plastic wrap. I cannot think of any other way to minimize the off gassing with this tank (oh, and I do have a DIY Rex Grigg style reactor).
For a while there, the tank was not putting out enough actual CO2 bubbles...the controller was working well I guess. It kept the PH at 6.5, but I still wasn't getting the amount of dissolved CO2 that my plants needed. Then I discovered the relationship of Kh to PH to CO2! Aa-ha! My water consequently is very soft. So, I figured that I would need to "trick" the PH controller by adding baking soda to the tank and raise the KH/PH, and therefore the controller would then open up the "flood gates" so to speak, and release a lot more CO2 in order to drop the PH back down to 6.5 (PH only went up to maybe 6.8). All of this has happened in the last week. But now, I have noticed that the PH is still fluctuating and the CO2 gass is pumping out like crazy and the hardness is lower. Why isn't the CO2 dropping the PH back down to its set point?
My tank is 75 gallons. I took measurements this morning of both my aged tap water and current tank water. Here are the parameters:
Aged Tap: Tank:
PH - 7.5 PH - 6.7 (why not 6.5 as set?)
Nitrate - 12.5 Nitrate - 12.5
Nitrite - <.3 Nitrite - <.3
Ammonia - 0 Ammonia - 0
GH - 2 GH - 3
KH - 2 KH - 3.5/4
Phosphat - 1 phosphat - >2 (probably pretty high)
Iron - 0 (need to dose!)
Let me know your thoughts, I would greatly appreciate any advise! I will upload pics soon hopefully.