Water keeps buffering to 8+ PH

[rawprawn]

For 18 months I've been struggling to lower the PH of my cherry tank, but no matter what I do it ends up back at 8.4 on my meter/8+ with my API kit.

Last major check about a week ago:

 

PH 8-8.4

TDS 200ppm

GH 7

KH 5

Ammonia/Nitrate/Nitrite all 0.

 

The tank has been running for 18 months almost and all looks well.

 

Substrate is Serenity Black Diamond sand, filter medium is some bio balls that came with the cheap cannister filter I bought and topped off with ceramic noodles from Guppies.

 

As the tap water is also a very high PH here, I've started using pristine rain water from a farm in the upper Hastings valley (PH 5.6) with the prescribed 2 spoons of Saltyshrimp GH/KH per 20L, which seems to bring it up to 7.2-7.4 PH.

 

I've done about 6 weekly 20L/10% water changes (4 foot tank) with this water with no change whatsoever in PH, last time I did 40L.

 

It sticks so solidly at 8.4 that I'm concerned something is buffering the water.

 

I've got some of the sand from the tank in a container with RO water which is showing no change, but I'll give it 20hrs and check again against a control sample which is 7.4.

 

Only other thing I can think of is my driftwood, which is a big 2m piece I found on the beach and cut in half, then pressure blasted before I set up the tank. It's been there from the beginning and is covered in java moss.

I've got a couple more small peices from the shop that had and Anubia on one and Java fern on the other.

I'd have thought this much wood would have made the water more acidic.

 

I really don't want to get into PH up/down drops, I'm much more into letting the tank find its own ph level, but this seems odd.

 

I'm an instrument tech and all my gear is calibrated. It's not that.

 

Any suggestions what I'm looking for here?

 

Cheers.

 

 

 

[perplex]

id test your sand like your doing, i had that issue, i just left it over night in a super small amount of water, make sure you give it a good wash with the water that is your test water, check the ph before, then 1 day later

 

your rain water is 5.6ph? thats abit weird for rain water i thought, TDS must be higher in it than normal

 

how long have you had the drift wood in the tank soaking?

[rawprawn]

Cheers for the reply.

Yep, rinsed the sand in the test water thoroughly, and it looks like it might be changing the ph already after a half hour.

My thoughts exactly, I'll check again am.

Pure rainwater is slightly acidic due to some sort of ionization or something as it falls. I certainly don't claim to be an expert on that, but I did check with mr Google:

https://www.google.com.au/search?client=opera&q=natural+ph+of+rainwater&sourceid=opera&ie=UTF-8&oe=UTF-8

The driftwood has been in there over a year now.

Edited January 20, 2016 by rawprawn

[fishmosy]

Rain dissolves CO2 which makes it slightly acidic. In industrial areas, it dissolves pollution making it very acidic. 

[perplex]

2 hours ago, rawprawn said:

Cheers for the reply.

Yep, rinsed the sand in the test water thoroughly, and it looks like it might be changing the ph already after a half hour.

My thoughts exactly, I'll check again am.

Pure rainwater is slightly acidic due to some sort of ionization or something as it falls. I certainly don't claim to be an expert on that, but I did check with mr Google:

https://www.google.com.au/search?client=opera&q=natural+ph+of+rainwater&sourceid=opera&ie=UTF-8&oe=UTF-8

The driftwood has been in there over a year now.

yea, just see what it is like in the morning, give it abit of a mix before you test since the water wouldnt be moving

[rawprawn]

Yep, straight up to 7.9 overnight.

Fairly safe to say it's going to be at 8.4 soon enough.

So much for Serenity's BS claims of its sand being inert. Bloody frustrating as the whole time I'd dismissed the substrate being the issue due to what I was told when I bought it.

Not sure how to play it from here....

I was already going to set up a second tank to improve my cherry line, but I'll probably move the lot now.

I must say the thought that has crossed my mind is that this would make a good Sulawesi Cardinal tank....

Can anyone confirm that Piscies NZ Black Iron sand is inert??

I'd hate to buy a load of that and have the same thing happen.

 

 

[s1l3nt]

Yes, Iron Sand is inert. I've got it in a few of my tanks without issue. Be careful with magnet cleaners near it though...

[perplex]

2 hours ago, rawprawn said:

Yep, straight up to 7.9 overnight.

Fairly safe to say it's going to be at 8.4 soon enough.

So much for Serenity's BS claims of its sand being inert. Bloody frustrating as the whole time I'd dismissed the substrate being the issue due to what I was told when I bought it.

Not sure how to play it from here....

I was already going to set up a second tank to improve my cherry line, but I'll probably move the lot now.

I must say the thought that has crossed my mind is that this would make a good Sulawesi Cardinal tank....

Can anyone confirm that Piscies NZ Black Iron sand is inert??

I'd hate to buy a load of that and have the same thing happen.

 

 

i had the exact same issue, it said it was neutral ph, but it wasnt.... and i thought the same thing, testing everything else but the gravel...

 

what i did to make sure my gravel is inert, since i wont trust what they say now, is find a fish shop that has gravel out of bags, find some you like and see if you can take a handful home to test

 

 

[rawprawn]

Must say I'm not at all impressed with the Serenity sand, which is still sold today as inert.

As a noob I've fallen into the trap of believing them, and with the local water being known for being very alkaline, I've searched for other reasons for ages.

It was only when I started adding low ph water and saw it rebound to precisely the same place over and over that I started to wonder about buffering....now I know.

Just got 2x 20kg bag of iron sand from the local Petbarn for 45 bucks each.

I've found a cheap 5 footer with a canister and I have a spare chiller, so now it's a matter of setting up and cycling a new tank.

Lessons learned.

[perplex]

just test the sand anyway, never hurts