My pH is low while cycling. Should I do anything?

[Arwen Vaughan]

I am fishless cycling a 150 gallon IBC tote with ammonia. It is day 7 and no traces of nitrite or nitrate. In the last few days the pH started dropping and is now at 6.2. I am trying to take the advice I keep hearing to do nothing and just be patient. So, I am asking for advice before adding anything. I guess there are no fish, plants, or bacteria yet, so...hang tight or add something? I bought a little calcium carbonate and potassium bicarbonate in case I need it. What do you think? 

[Eric Warwick]

Man, if buffers were easy for you to understand in High School, then you're a freakin' genius. Everyone in my AP Chem' class was frustrated for about a week on the subject. (Probably because the teacher didn't outright say the answer--so we could figure it out ourselves.) Anyway, what Vlad articulated is what I trying to say, so listen to him. In your situation, KOH is ABSOLUTELY the best base to add, however buffers are hard to come by, other than carbonates. Yes, the place will matter, because some areas have a large buffering capacity in the water.

As for titrations, those can go horribly wrong if you're given bad materials (ex. the titration lab I did last year--it's even become an inside joke among my friends). However, they're not terribly complicated, and there are plenty of instructions online. Sorry if I'm vague about things, by the way--water just doesn't belong on top of a keyboard. LOL

[Arwen Vaughan]

Hi Vlad. I got a better liquid drops test kit for hardness because the little paper strips were such crap. So here are the new, more accurate, numbers for my water after 13 days of cycling...

General Hardness (GH) = ~400 ppm

Carbonate Hardness (kH) = 0 ppm

pH = 7.2

Ammonia = 2.0

Nitrite = 0

Nitrate = 0

Still no sign of nitrites and the carbonate hardness is 0 ppm, while the general harness is like 400ppm. Anyway, I was thinking of adding more ammonia to get it up to around 4.0 and adding more calcium carbonate / potassium bicarbonate as well. Can general hardness be too high? Should I be seeing nitrites by now....or just give it another week? Wow, aquaponics takes a lot of patience. :)

Cheers

[Vlad Jovanovic]

Arwen those numbers seem a little off to me. Certainly not unheard of or impossible or anything...just a bit off.is all. If we accept the premise that those are the numbers...you really need to get your kH higher (to between 60 to 100ppm). Don't worry about your pH right now, forget what you think you need/want ( a pH below neutral is gonna make it tougher for your bacteria to get going, and if your kH is still truly zero, that will make it even harder. Trying to keep a low pH right now is counter productive, particularly because of your water quality parameters...so just totally forget about the pH for a minute and get that kH up a bit).

Your ammonia is absolutely fine...but it is utterly useless without some degree (above 40ppm) of carbonate alkalinity (kH).

I'm going to assume you have a kH test where you add 1 drop of reagent to 5ml of water...it (should) turns blue, then you add an additional drops, counting how many it takes until the water turns yellow.  ...And that in your case, after the very first drop, the water is turning yellow instead of blue...meaning you have a kH of zero. Correct?

[Arwen Vaughan]

Yes, the kH test turned yellow with the very first drop. The GH test was off the scale before turning green. I added 21 drops but the scale only went to 12 drops, which it said corresponds to a value of roughly 200. Why is the general hardness off the chart and carbonate harness still 0? I know I am doing the tests correctly. Is Denver water just super soft or something? I'll keep adding calcium carbonate and see if I can bring it up.

[Vlad Jovanovic]

Ok, I was just checking. Yup, add the potassium bicarb and/or calcium carbonate (the potassium bicarb is, IMO at this junction a slightly better choice...but either way get those carbonates into the water :)

gH is just a measure of the divalent metal cations in your water (usually mostly Mg2+ and Ca2+) 

[Arwen Vaughan]

Vlad,

I just wanted to give an update...

I did exactly what you recommended and it worked. I alternated adding KHCO3 and CaCO3, and as soon as the kH got up to around 50 ppm I started seeing nitrites. Then a day later I started seeing some nitrates. And now the ammonia has dropped to almost 0 ppm,  nitrites are greater than 5 ppm (test kit stops at 5), and nitrates are about 80 ppm. So I am thinking it will be just a few days now before I can add some fish...perhaps this weekend.

My understanding is the nitrites will keep on converting to nitrate and I can add the fish once the ammonia and nitrites are nearly 0. Can there be too much nitrate though? I don't have a lot of plants yet so the nitrates may not be used very quickly.

Thanks again for your help.

Arwen

 

[Vlad Jovanovic]

...Glad to help Arwen. Now just keep an eye from time to time on that kH and buffer accordingly.

Once you can dose to around 1ppm ammonia and within 24 hours have both ammonia AND nitrites be down to zero, and you can do this consecutively for 3-4 days, you are ready for fish. (Do yourself a favor and don't overstock your system, or if you are going for a maximum type stocking density right away... at least pre-preemptively salt the system to deal with the (secondary) nitrite spike that will likely ensue.

Don't fret about too much nitrates at all...it's unlikely that you'll ever come anywhere even close to those numbers, but yes, you can in theory have too much nitrates (or anything else really). The sphere of aquaria seem to have a different opinion about where those numbers lie,  than the RAS (re-circulating aquaculture) folks. Kinda the way Vegan's have a different opinion from even the the Free Range Daiy Farmer...IMO, it's not a realistic concern for you.

[Arwen Vaughan]

Vlad,

Well I am three weeks into this cycling business now. It is looking pretty good but still not quite there. I have nitrites > 5 ppm still and now the nitrates have dropped substantially. Is this normal. I was expecting the nitrites to drop and nitrated to continue going up, but perhaps the plants are just sucking up nitrates that quickly? Here is my water testing history. Please let me know if anything looks out of the ordinary. Maybe my nitrate test was just a bit messed up...so I will test again tonight.

http://homebrewaquaponics.blogspot.com/ 

[Vlad Jovanovic]

Hi Arwen...That all looks pretty on the up and up...The nitrite spike can last a good while. I would not worry about it at all, since you don't yet have fish in the system.

You could comfortably dose a bit of ammonia again (1-3ppm) and just let the bacteria do their thing. These guys are really, really, REALLY slow (as far as bacteria go) to multiply.

Don't worry at all about the nitrates dropping at this point...

It's very, very cool to see that you are keeping track of all your water parameters...Wish that more people would do that