pH Dropping Dramatically During Cycling

[Bradb90]

Hey everyone,

I have a question concerning my water parameters during my cycle. I live in NYC and have pretty soft water out of the tap. 6.8 after sitting and about 30 tds.

I am in my 3rd week of my cycle. I seeded with Seachem stability and it seems to be working. The bacteria can completely convert 4ppm of ammonia daily. So I dose every day to keep the cycle going. However, I have started to notice pretty dramatic drops in pH, from 7-6.3 in a matter of hours. I have an Apex controller on my tank so I can see pH changes in real time and back this up by testing with my API master test kit.

I have noticed my Nitrites have begun to drop slowly, but my nitrates are really going anywhere. I assume this has to do in part with the plants?

I understand that the nitrification process consumes alkalinity at a rate of 7.1 mg/L per 1 mg/L of ammonia and that the nitrification process stalls at a pH of 6.

I'm trying to figure out if bringing my kH up to 5-8 would help stabilize these pH swings and if this is a normal occurrence.

kH: ~2-3
GH: 5
Ammonia: 4ppm
Nitrite: 5ppm
Nitrate: 5ppm
pH: 6.5
Temp: 85

Some info about my tank set up:

- 72 gallon display w/ 30 gallon sump.
- Planted with Java fern and anubias/Manzanita
- Inert white sand
- I run a reactor for Purigen
- UV sterilizer is currently off
- I use tap but treat with Prime

Please let me know if there is any additional information that I'm leaving out to help solve this issue.

Thanks

[captainandy]

Stop dosing with anything. Sounds like you are already cycled.
Your pH will settle down.

[coralbandit]

You say the tank processes 4ppm of ammonia daily . When the ammonia is 0 what are your nitrIte and nitrAte levels ?
Ammonia going to zero is only step one you still show nitrItes ..
I learned fishless cycling with cutting from 4ppm to 2 ppm ammonia once nitrItes show since 1 ppm ammonia converts to 3+ ppm nitrItes to allow the next bacteria to catch up without being overwhelmed ?
Most don't change water in fishless cycles so your pH drop may be from not changing water ?
Are you changing any water and if so how much ? You say tap with prime ,how often ?
If you are running purigen then all your numbers may be skewed ??Have you had to re charge it yet ? I would pull the purigen till cycle is complete ...
Welcome to SD.
What do you plan on stocking [dumb question ?] ..

[dspeers]

Brad, this is entirely expected. You are adding a base ammonia, that is being metabolized into an acid nitrous, and its conjugate base nitrite and then nitric acid and its conjugate base nitrate. The lower the kH the wider the pH swing. To maintain a stable pH a minimum kH of 5 is usually recommended. Certainly lower if breeding but then you need more frequent water changes to avoid pH bottoming out. I fully endorse Coral Bandit (not hard, he is wiser than I) in re dropping your ammonia dosage and allowing your nitrite eating bacteria to catch up and when both ammonia and nitrites are zero within 24 hours, do a big water change to drop your nitrates and add fish. What did you mean about nitrates and plants? "but my nitrates are really going anywhere. I assume this has to do in part with the plants?"

[Bradb90]

Thanks for the responses.

I've only done one 50% water change to keep my pH from going below 6 as i didn't want to stall my cycle. I normally don't touch my tank during the cycle, but couldn't let it get that low and my bacteria start to die off. Before I did anything when ammonia disappeared my nitrites were off the chart. Nitrates were at 5-10ppm still. I know the cycle is not finished because the Nitrites haven't disappeared yet, but this may be because I was dosing 4ppm ammonia per day. I'm not going to dose for a bit and see if they drop.

Plants, during photosynthesis also uptake nitrates and ammonia as a food source, this is why people use plants in their refugium, but normally it's fast growing plants such as water wistera or cheato in reef tanks, so I doubt my java fern and anubias would affect it much now that I think about it.

Purigen on the other doesn't really disturb the cycle as far as I know. It does remove dissolved organic compounds but not enough to stop the beneficial bacteria from getting what they need first. I have been running it since day 1 and my cycle has gone pretty fast so far, I also don't run a heavy flow through it because of that reason.

I mostly run it because I didn't like the yellow tint from my Manzanita. I think it's done leeching now though.

I have changed my purigen once and replaced it with new while regenerating the old. It's finished now and just drying, gonna test to make sure there are no remnants of chlorine (I did soak in fresh water for 24 hours, then followed with another 24 hours with treated water (prime)).

I ordered 6 - 4.5-5" discus from Kenny to start with but I don't plan on adding anything else for a while after that.

On a side note is definitely interesting seeing life starting to pop up. There are copepods all over my glass eating algae.

[Shan_Evolved]

I also have soft water with a KH of 1.

If it wasn't for baking soda my Ph would crash during a cycle.

I used 2 tsp of baking soda to get my KH up to 4-5. After that the initial dose of 4ppm ammonia + bottled bacteria. The trick here is to wait for not only your ammonia to drop to low numbers but your nitrites too. My mistake was dosing ammonia when it dropped instead of giving the nitrites a chance to also drop. I also closely monitored my levels and my KH would drop 1-2 degrees in 1-2 weeks .

I personally wouldn't cycle with any chemical as well besides bottled bacteria and dr tims ammonia

[Bradb90]

Yes, I actually slowly dosed baking soda to bring my kH up to 3 over the course of 3 days. I seems to have stabilized now my ph hasn't changed for the last 8-10 hours. My tank took care of my last full ammonia does of 4ppm in less than 12 hours, so I am stopping dosing anything now that everything seems to have evened out a bit.

[AquaticNerd]

I wouldn't stop dosing ammonia completely unless you already have fish ready to add.

If your tank has completely cycled and can handle 4ppm of ammonia in about 12 hours, I would cut back the amount of ammonia you dose to half or maybe a quarter of what you've been dosing. This will prevent the BB from starving and dying off, which would more than likely result in a "mini-cycle" come time when you add your fish. I did this when I was cycling: 4PPM ammonia during cycle, and 2PPM after cycle complete. 1PPM in AM and 1 PPM in PM so the BB were "fed" and didn't starve over an extended period of time (like if one was to dose 2PPM in the AM and then wait a full 24 hours to dose 2PPM). Large (90-100%) WC right before fish takes care of built up Nitrate, but I always did a WC if my nitrates were over 150.

[fljones3]

This is controversial and anecdotal. I used purigen for a couple of months and did find it reduced PH slightly. Your major contributors have already been pointed out above. However, you might want to monitor your usage. Your experience may differ.

[Bradb90]

It seems my pH has stabilized now. It is currently 7.34. It drops down to 6.5-6.8 when I dose 2ppm ammonia then comes back up to the 7.3ish range after a few hours. Raising my kH to 3 seems to have fixed this issue. Thanks guys.