KH is OK, but PH is waaaayyyy low...help?!?

[29gallonsteve]

Hopefully, someone can shed some light on the phosphate/KH/pH relationship for me...(assuming there is one).

Moderately planted tank with heavier fish load:

29g freshwater
MgSO4 - dosing at 0.8ppm/ml daily
K2SO4 - 1/4 tsp at 25% water change (weekly)
pH - 6.0-6.4
KH - 5.5 dKH
GH - 14 dGH
CO2 - DIY injected with gravel vac
PO4 - 0.5-1.0
NO3 - 10ppm

Feeding fish moderately every-other day.

Why is my pH so low? Considering no other factors other than CO2/pH/KH, my CO2 concentration is approx 93+ppm...

My fish display no signs of toxcicity, breathing or stress. As a matter of fact, the other day I think I caught my two gold barbs working on a mating ritual!

My test kits are fine...my 'out of tap' for pH is 7.0+ (didn't test PO4 or KH/GH of tap - guess I should).

Any help or advice? Is my PO4 level (with some other nutrient missing) causing a drop in PH???

Forgot to mention that I have very light filtration Penguin 125 with sponge filter material blocking the outlet (to prevent surface agitation).

Thanks,
Steve

[djlen]

Steve,
Do you have any wood in the tank? Driftwood or African Root can cause pH readings to be way off. I use 'Root' and according to my pH test kit I have close to 70ppm/CO2, which I know is bogus cause the fish are fine.
A question for you. You have relatively hard water. What is the reason you add MgSO4 every day? Just curious........
Len

[29gallonsteve]

The MgSO4 is for the plants (magnesium - macro ingredient).

Correct me if I am wrong, but MgSO4 would only effect the GH, not KH, right? If that is correct, am I safe to assume that GH does not effect KH?

BTW - No root...only Profile, Pool sand, shale and aq gravel...

Thanks,
Steve

[Faramir]

Any peat or bogwood in here? Any organic acids will depress the pH. Although they also depress the KH, the effect on pH is direct as well as through KH.

[29gallonsteve]

I have had crypt melt lately (tried to transplant some of them) and recently jacked up my co2 production (I use standard mix instead of Jello)...but nothing added to the tank that could contribute to shift (that I can think of).

I am also dosing Seachem Iron and Flourish 2-3 times/week @ 1.5 ml per dose.

Thanks,
Steve

[29gallonsteve]

Here's a thought (actually, I just read something out there)...

Since I slowed my filtration down, would the carbonic acid created by degrading fish waste cause my ph to go more acidic???

Thanks
STeve

[djlen]

Something is giving you a mis-reading on your pH. I suspect your test kit unless there is something in the tank that is depressing pH that we haven't thought of.
MgSO4 is not a macro. IMO, you don't need to dose that much with your hardness values.
Meanwhile, I would increase your dosage of Flourish to 5mls, twice a week. That will take care of your Traces. What Macros are you dosing(N,K,P)?
Yes, either contact your water supply company and ask for print out of what's in your water. Or at least test for as many elements out of the tap as you can. For some tests like pH it is a good idea to test out of the tap and then leave the water sit out over night to gas off and then test again. You will probably see a difference.
Len

[29gallonsteve]

Len,

I am still confused...(I know, very unusual)...

Here are the responses...

---"Something is giving you a mis-reading on your pH. I suspect your test kit unless there is something in the tank that is depressing pH that we haven't thought of."

I have run some comparative testing with my tap...it still tests the higher pH levels, so it is not the test... my out of tap is 7.0, but the outgassed ph is around 7.5 (tested it before).

---"MgSO4 is not a macro. IMO, you don't need to dose that much with your hardness values."

My fault...it is micro, but I think that the reason my GH is high is bc of my dosing.

---"Meanwhile, I would increase your dosage of Flourish to 5mls, twice a week. That will take care of your Traces. What Macros are you dosing(N,K,P)?"

Seems like alot of Flourish, don't ya think (concerned about algae). Dosing N as needed (although waste keeps it at 5-10ppm), K2SO4 1/4 tsp every water change, P is at the right levels (due to fish food and water changes)...

Thanks,
Steve

[djlen]

Only you can determine what's right for your tank based on your fish load and plants.
With regard to Flourish, I dose 10mls. in one of my 55s and my 40(both 3watts/gal., moderately planted), 3x a week. I dose 10mls 2x a week on my other 55(1.5 watts/gal.) moderately planted. And 10mls., 1x a week in my 10(1.5 watts/gal.). This works for me. I have found that the only fert that actually causes me problems with algae is Iron when I dose too much, and that's just that green spot stuff that can accumulate on glass.
Recently, I noticed the beginnings of BBA in my higher light 55. I cleaned it up, upped the CO2 slightly, and dosed heavier on the KNO3 and slightly more on the PO4 and it's cleared itself up.
It's hard to overdose on K and Traces so I push the envelope and so far it's worked. And my safety valve is my 50% water change every week.
I hope Tom responds to your thread. It'll be interesting to see his take on this.
Len