Bad Rock Decor?

[TheSugarBear]

Hi all! Brand new here.

I just setup my tank three days ago. It's destined to be a planted tank. It's a 55gal long. I used 3" of Eco-Complete and about 1/2 of regular brownish pebble aquarium gravel over the top of it. I used RO/DI water for all of it. 2.5watts/gal for 8 hours of the day and 5 watts/gal for 4 hours of the day. There are 4 adult angels, 15 adult tetras, 2 Otto's, and 2 small plecos.

It was a used tank and the brown gravel was used in part to seed bacteria (even though Eco-Complete claims to contain all I need).

My problem is this:
An hour after setting up the tank it had a pH of 6.5 - perfect!

Today, 3 days later, the pH has risen to 7.5 - not so good...

N3, N4, and NH3 are all so low they don't even register on the tests. I don't yet have a KH test kit so I can't give that one.

So now the meat of my question: I am trying to figure out why the pH is rising and suspect the two pieces of rock decor that came with the tank. Can someone ID what kind of rock this is and tell me if it (like coral) is suspect in raising my pH? I hate to get rid of them because the fish love them - but too bad if they're the cause of my woes. I just got my DIY CO2 system seeded and running today and I know that should help a bit, but I need to know about these rocks.

Thank you.

 

[rich311k]

Before you start ripping rocks out etc. Have you left a glass of tap water out for 24 hours and then tested the PH? It could just be CO2 gassing off. As for the readings do you have any fish or source of ammonia to start a cycle?

 

[TheSugarBear]

I have about 20 fish in the tank. Some of the gravel that came with the tank was used to seed the bacteria. I haven't tested a glass of sitting water yet. I used Reverse Osmosis and De-ionized water not tap water. I still have some left over and can test that.

Can anyone ID that rock and say if it is a problem in acidic tanks?

 

[rich311k]

Take the rock out put it in a bucket of water and test the PH over the course of a week or two. You will isolate the rock that way and know for sure. Just curious did you add anything to the RO/DI water? Plants will need a little GH booster.

 

[Sidi]

Hmm, it appears to have too much color to be straight typical limestone (or chemically deposited limestone). It does appear to be sedimentary though, assuming it's natural.

Unfortunately, I doubt anyone will be able to truly identify it further without without an acid test. Limestone makes up much of sedimentary rock, or it could be any of dozens of other whitish minerals. Try throwing some vinegar on the white sections and look for bubbling.

Did you do anything to reconstitute the RO/DI water afterwards? The lack of buffering might mean that almost anything (including the rock) could cause a pH shift...perhaps even the plants consuming CO2.

 

[TheSugarBear]

Thanks for the replies.

Good suggestions on the rock. Thank you.

No I did not add anything back to the water after the RO/DI processing. Can you suggest something? I am shooting for a S. American tank? Right now I only have the Java Fern that came with the tank and that will go once I get the tank in shape for new S. American plants.

 

[Fishyfanatic]

Just curious, but is there a reason why you are using RO/DI instead of straight tap?

 

[An t-iasg]

In addition to isolating and checking the rock -

Is the Eco Complete new or used? New Eco will buffer, and probably increase, your GH and KH values. My GH and KH rose a few degrees from my usual tap water reading. The effects in my tank lasted about 6-8 months.

 

[TheSugarBear]

@Fishyfanatic - I used RO/DI instead of tap to eliminate phosphates from the start. Our tap is straight from a river flowing out of the Cascade Mts and has a decent amount of all minerals in it. I guess I didn't do my research well enough to consider the buffering needs. I got the whole RO/DI thought blazed into my head years ago while doing marine tanks. The difference is that the salts that you mix with the RO/DI in a marine application include buffers. I'm definitely still learning...

@An t-iasg - The Eco Complete were brand new and looked great. I have five bags of it in the tank. I do remember reading that it conditioned the water and made it take on the characteristics of "black water" and that sounded good. Not sure why that isn't happening. The rocks were isolated last night. Haven't run the test on them yet (more specifically the water I placed them in) to see if they are a problem or not. I am also going to re-test the tank to see if it has had a change since the removal of the rocks.

Thank you all again for your help!

 

[Fishyfanatic]

I doubt the rock that you have is going to alter the pH. I have the same ones in my 150 and 55 gal tank. Then again, my natural pH is off the charts. I don't seem to remeber a change when our pH was at a low 7.0 level though.

 

[TheSugarBear]

You're right. It's not the rock. I'm leaning toward the lack of a buffer in addition to the plants using up the CO2 as the causal factors. I'm going to work on bringing the pH down with peat and the addition of a "discus buffer" I bought at the store today.