Black Gravel, should it affect PH

[Frontyking]

Hello guys,

I bought some black gravel to use as substrate on the weekend from a LFS, but before doing so I was tossing up between that and sand. Once I found out that sand will more than likely raise my PH, I asked about the gravel and was told that it won't raise the PH. This substrate is intended for a catfish only tank, hence the reason why I want to keep the PH down.
I brought the gravel home and got stuck into cleaning it out straight away. After cleaning it for about an hour(only 7 or 8 kilos of it) when you couldn't get it any cleaner, I started cleaning it again just to make sure that it was clean. With that out of the way, I think I have ruled out any possibility of it not being cleaned enough to keep my PH up at 8.0-8.1 when I need it to be around 7.0-7.2. I used Ph down that afternoon to get it down to 7.5. When I checked it this morning it was back at 8.1. I gave it another hit of PH down and got it to 7.5 and again this afternoon when I got home I found it at 8.1 again.

In the tank there are also 2 half pots(9 inch ones) and a medium piece of bogwood(about 1/2ft long and 1/2ft wide with anubis growing on it.

I don't want to drop the PH quickly as I'm worried I might shock the fish that are in there. Is it the black gravel or is it something else Water parameters are ammonia, nitrite, nitrate = 0

Any ideas guys?

Thanks,

Nick.

[Alistair]

It sounds like something in your water is acting as a pH buffer. In theory if your black gravel is true aquarium gravel it should be inert and therefore not affect the pH, have a closer look and see if there any rogue pieces of coral sand/gravel. If this is not the case, take som of the gravel out, dry it, put it in a cup and add some spirit vinegar or citric acid. If it is basic (high pH) it will effervesce (fiz).

If this draws a blank check the pH of your water? I have heard of water companies dosing their supply with buffers to prevent damage to their pipe lines, if this is the case you would have to use lots and lots of pH down to reduce the pH of the tank water (not advisable as ou could end up with an interesting mix of all sorts of salts and ions in the water) so you would be wise to invest in an RO unit to if you want to reduce the pH and eliminate the buffers from your water,remember to back dose with trace elements to replicate true fresh water though.

[Frontyking]

Alistair you're a legend.

Problem solved guys, it is the gravel. I covered some gravel in a cup with some vinegar and low and behold....BUBBLES. The gravel contains calcium so therefore it raises the PH. I won't be taking advice from that LFS anymore.

Any other recommendations on substrate? Pebbles maybe? I don't really want to use sand for obvious reasons of PH instability.

Cheers and thanks for your input!

Nick.

[Frontyking]

In regards to using RO water, I looked into it I was told that my Zebras are too young and that it might result in death. They are all around the 3.5cm mark. Would this be true?

Cheers,

Nick.

[Alistair]

Only to happy to help. RE the RO water, I heve never heard of that one but then again I have never used it personally as my domestic water is spot on (lucky me!). But now that we have identified the gravel as the offending item you shouldn't need to use it.

As for sand affecting the pH, again this should be just silica sand which is inert and will not affect the pH. Some people prefer sand (the guys recommend kids play sand as it is ready washed and cleaned) others use dark gravel and some insist on abare bottom! Just personnel preference. I prefer fine gravel myself.

Just a quick note on using sand, becuase it is so fine it can compact down and trap organic detritus. If left undisturbed this can lead to anaerobic bacteria in the sand which is not good as the produce some noxious gasses from the breakdown of the waste. Look for the comments on using snails to turn the sand over and prevent build up.

[thebuddy]

your not supposed to say LFS its slang or so ive been told by a mod/admin (whats the differnce)

[Mindy]

I have aquarium sand (silica) in most of my tanks and it does not affect the pH at all. Other people buy play sand and builders sand and stuff to save a little money, but I just stick with the aquarium sand because I'm sure of what it is and what it's intended for. But that's just me.

[october004]

I am not an expert but from my zebs I have had some young ones and they never were hurt by ro water. Just thought I give you my 2 cents.