Sand Buffering Problem?

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Dylema

Feeder Fish
MFK Member
Sep 28, 2010
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Adelaide, Australia
I am trying to find some fine white sand for my new 75g tank which is proving very difficult to find. Over the last month I have had some play sand in a 10g tank with a bit of wood a few plants and a couple of tetras as a sort of a test run for the substrate.

Well the pH from the tap water is about 7.6 and the kH is about 3 points. Well the pH has crept up a little to about 7.8 and the kH is now up to 6 points. I suspect there is a little bit of coral sand in there as I found a few traces of coral when I was cleaning it prior to setting up the tank.

My tank is going to hold South American's Cichlids, tetras, Pleco. so I want a low pH/kH value. I have successfully buffered down the tap water before using wood and peat and this was my plan but I am not sure how successful this will be if the substrate it buffering up.

Can anyone help with a solution to keep the pH/kH a stable low value using this substrate.

Thanks

Dylan
 
It depends 100% on if the substrate is actually buffeting. Your water will naturally adjust to its "true" ph after aging and gassing off for a couple days. Have you measured your tap water outside of the tank after it has sat for a couple days with something like an airstone? You can also use this method to test the buffeting capacity of the substrate... Do the first test, add a handful of substrate in, test again after 24-48 hours.
 
You might be fretting over a non issue.
You would be amazed at how fish can adjust to water conditions outside of what the “BOOK” says.
Over the years I have found fish will do much better adjusting to the water from my tap than they do in water I have to chemically alter.
You have given thought to what the fish might do to fine sand?
I had it for a very short time.
Every flip of a tail sent clouds of sand into the water column.
From there it made it`s way into the filters.
It only lasted a month or so, before I pulled it out and used a heavier grained sand.
 
Thanks for the replies. aclockworkorange, I will try that test, I have only tested the water straight from the tap and then when it has been in the tank a while not in a bucket after a day so I will see what happens to it then.

KaiserSousay, I am very much interested in keeping a stable system rather than an ideal pH, and I am not keen to be adding chemicals (pH down etc) to keep the pH where I want it, but I think that a pH near 8 might be pushing the limit of reasonable conditions for fish that like pH 6 or lower with almost no hardness. basically I think if the pH is less than 7 I should be fine.

I am really having a hard time finding any white sand regardless of grain size. My next best option is a light coloured river sand from my LFS that is a much bigger grain size but is mixed colours ranging from white to light brown. I think that is about $40 for a 25kg bag so it is not cheap. For pure white fine rounded quartz sand the LFS is asking an obscene price of $70/5kg which is simply out of the question. Play sand is $10 for 20kg or in bulk from the landscape supplier it is about $40 for literally half a ton.

Has anyone used water softening resin in filters before? I was told that might work but I have never had any experience.

Dylan
 
Pretty much your only real option if you want long term stable results for lowering ph/kh is to invest in a RO system.
 
Well it has taken me a while to get back to this issue. I appreciate that RO is really a good way to have reliably soft water but I don't think it is necessary in my case. Also if I had a substrate that buffers the water into the alkaline range then RO would not help, in fact it would probably cause problems putting soft water in a tank only to have the pH rush up. I will have a new large rainwater tank installed by the time this tank is stocked so I will actually have a good source of soft water.

Well I have tested the water and substrate. I had water running through my empty 75g for a month or two so that gave me a baseline for well de-gassed tap water. the results say pH 7.6 or higher (test limit) kH 3. Tank with the substrate pH7.8 (tested at LFS) kH 6. I put some peat in for a week and had no measurable change in pH or kH. I took some water from the 75 and pulled the pH down using 0.5ml of vinegar in 1lt of water which took the pH down to 6.4. I put 250ml in two glass jars one just water, one with 250g of sand. After about 12 hours the jar with substrate reads at least 7.6 and the jar without 7.0. Which I think shows pretty clearly the substrate will buffer up the pH. The final piece in the puzzle (and easiest), I got a bottle put some sand in it, filled it half way with vinegar and fizz, it bubbled violently like bicarb and vinegar does.

So that basically means this is not a suitable substrate for me.

Dylan
 
I would say you've proven your substrate is buffering. However, unless your fish are wild caught and prefer extremely low ph, you should not have a problem keeping almost anything (some would even argue that even wild caught SA fish can do fine in that ph/kh). Would also be a great excuse to keep central american or african cichlids.
 
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