911 pH emergency

Hi all!

I have a fully cycled tank (had my water tested at local aquarium shop) my pH is registering at 6.0
ammonia .25 or a bit less
NitrAte 0
Nitrite 0
water temp 66F-68F/19-21C
Tank is 20L with HOB power filter for up to 30 gal
Sand substrate, Anubias, and java fern, and three marimo balls
One 8" long 2" wide African drift wood log with attached Anubias

48 hours ago I added a bit less than a tablespoon of crushed coral on LFS advice
I also tested my tap water after adding stresscoat to dechlorinate and it reads at 7.4-7.6
So! Yesterday I changed about 50% of the water VERY gradually about a half gallon at a time over about 8 hours

I tested every few gallons and saw an increase to about 6.4 - I am not sure how low the pH actually fell due to it registering at 6.0 and that being the lowest on the drop kit

I tested this morning and it had fallen a bit maybe 6.2 - VERY light green on test

I did an additional 35% water change throughout today -- it is back to 6.0 or there about

If my tap water is high pH WHAT could be dropping the pH so quickly in my tank!?

I have included photos of my set-up if you see ANYTHING that could be the culprit or have any ideas - I am begging for help.

I'm considering adding more crushed coral to the filter and removing everything and doing an almost full water change but don't want to break my cycle (though I do have a bottle of TSS just incase)

My big melanoid Totoro is happy and swimming and eating like a champ. My much smaller leucistic Ponyo is not eating (one tubifex at a time and maybe 4 or 5 for the whole day) -"and is very flaky looking and not growing very well - they are the same age but certainly don't look it -- we are almost in crisis mode for poor Ponyo if I can't fix this water situation.

Take out the driftwood log, do a large water change and then retest in a few days. If you have a big piece of driftwood in a small tank it can really change your water chemistry

First thing I would do is take out the driftwood. The tannins in the wood can drop your PH. Then do some water changes over a few days and see how that helps. Hopefully things work out!


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Thank you both!

I removed the driftwood and at least half of the sand. Cleaned everything very well and did a 50% water change. 48 hours later still no increase.

I added 1 tbsp crushed coral and fridged the axies while we wait.

Does anyone have anything to say about the sand? It's National Geographic brand black sand fine substrate. Could that be creating any issues?

I'm considering a bare bottom against my own preferences -- what could I use instead to create some grip for the little ones?

I haven't heard of that sand but if it is aquarium safe then it shouldn't be a problem. I use sand from my local beach (well washed several times in fresh water, of course) so this may be a solution for you.

You could also add something like texas holey rock as decor/hides:

Pisces Texas Holey Rock 10Kg

and then continue testing to see if this helps stabilise your pH.

Invest in an API Liquid matser test kit:

http://www.thetechden.com.au/API_Freshwater_Master_Test_Kit_p/aph41.htm

they are by far the most reliable.

TBH, I'm still a bit perplexed about what is actually causing the problem in the first place.

Update to my above post, I just googled your sand and found this warning:

'Substrate may contain minerals that affect the water pH. Monitor the pH of the water and adjust as necessary to avoid sudden changes.'

From this site: https://www.petsmart.com/fish/suppl...graphicandtrade-aquarium-substrate-21326.html

Scroll down and read under "product highlilghts".

This may be your problem - either way I would get rid of it completely - use play sand, pool filter sand or normal beach sand like I mentioned previously.

I use the exact same sand and my ph is still around 7.8. I personally haven't had any problems with it. I could just be lucky though. If you do end up deciding to replace the sand, slate tiles cut to size and siliconed into place have the benefit of easy cleaning but still give your axies something to grip.


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Felix, my friend who has two adult axolotls also uses this same sand with no ill effects.

I've done a full water change and removed most of the sand. I rinsed several times the remaining bit of sand that was left in the bag added it in to the tank and now I wait..

As of now, my pH is at 7.8 -- that's what comes out of the tap I'll monitor for the next few days and add in items as I go to see what might be causing the imbalance.

Luca, thank you for the pointers and the links!! Unfortunately, I do not live near a beach

no worries, I hope all is well with your little axie friends. Play sand or pool filter sand will be fine if you want to use it, just wash extremely well before adding to your tank