Updated 1-18-10

This article is a simple question and answer post between me and two customers that asked similar questions.

QUESTION:

One of these days I'm going to write down the chemistry for pH, kH and GH and maybe I will remember it, eventually. But for now I new some advice. I got many good suggestions on my fairly new mbuna tank and thus far it has been going very well but something is amiss with my water. My tap water comes out at about 7.6 pH. I have about 30 pounds of holey rock in there currently. But, for some reason my pH seems to be dropping. Currently it is approaching 7.2

My gH is still pretty high 200 or so, but my kH has also started dropping from around 120 to currently just under 80. Nitrates are between 10 and 20. 0-0 on the bad stuff. I am doing 30-40% weekly water changes. I have 16 fishes in a 55 gal between 1 1/2 and 3". I may need yet another reminder about water chemistry or could it be my 'mystery' substrate. Along with some small tan gravel which I have used in many tanks with no apparent detriment, I also have maybe 15 # of stuff that was given to me a while back along with my first cichlids, a little tank etc. I have no idea what it is but she mentioned it was "supposed to be good for aquarium plants". It is approximately 1/3 each of black, brick red and tan stone. Though relatively small they are more like little chips than rounded pebbles - fairly jagged and rough on the edges. Then again it may not be this at all. Any ideas?
Thank you.


ANSWER:

There is probably something producing a heavier than normal amount of acid production. The normal biological process of Nitrification will have the same effect of as to titrating with nitric acid nitric acid (NHO3), Carbonate hardness (KH) is slowly used up in this
process, reducing buffering and pH. When the KH is completely depleted, you will find that the aquarium pH will stabilize around pH 4.4 (of coarse this is much to low), and if you have a large amount of organic build up that can be part of your reason.

What are your filter(s)? Some filters such as large canister filters can become what is referred to as “Nitrate factories” and in this process deplete KH (Carbonate Hardness) if not cleaned (rinsed) regularly. If you have an Under Gravel filter, make sure you occasionally remove the lift tubes and siphon out the mulm that accumulates under the plate. With all filters it is still important to remove as much mulm and other organic debris as possible, an Aquarium Vacuum is the preferred way.

As for your KH & GH, I am a big proponent of keeping an adequate KH (minimum 150 to 300 KH) and Calcium level for many reasons, one of them is for the problem you are having, the other is that GH is simple way of knowing your calcium levels in FW, and calcium is very important to fish health. Crushed coral or aragonite can help, but in my experience (especially in High ph aquariums such as African Cichlid tanks), they are not always adequate asthese substrates do not dissolve fast enough to release the proper amounts of Bicarbonates, Magnesium, or Calcium for KH and GH.

In the closed environment that an aquarium is, I find that outside sources that dissolve or are manually added are often necessary. There are many products available from SeaChem Malawi Buffer which is preferable to baking soda due to the balance of sodium bicarbonate/ magnesium and other minor elements; to the Wonder Shells which provide essential positive mineral ions (cations) necessary for fish osmoregulation.

At the risk of being too commercial, my personal and more importantly my aquarium maintenance client’s aquariums (especially Rift Lake Cichlids) are rarely without a Regular Wonder Shell for Calcium control and electrolytes.

As for the plant substrate you were given, this sounds like a product such as Eco Complete or Azoo Plant Grower Bed which will lower your pH.

I have an article about KH, Calcium and electrolytes: “AQUARIUM CHEMISTRY; Calcium, pH, GH, KH, Mineral Ions”

My point in mentioning GH was that Calcium and Magnesium is part of GH and
both are necessary for proper osmotic processes in fish. If there are problems with KH, many times there are problems with GH (although in this case there does not seem to be a problem). The problem here indicates too much organic decomposition thus reducing the KH.. Again I would check filters for build up too. When I called on customers aquariums experiencing this problem, many times they had a filter with a thick layer of mulch on the bottom. Removing this, then adding a KH stabilizer (which I had better results with a
slow dissolving KH stabilizer), and the problem was solved.

Carl
CALCIUM, MAGNESIUM, AND KH IN AQUARIUMS

QUESTION:
Carl, I am curious how the Wonder Shells compare per use with SeaChem Or Kent? I am definitely on a budget so sometimes I use 'good' at a Lower price, rather than 'better' at a higher price.
Does crushed coral, holey, aragonite, etc. buffer the water by actually dissolving, exchanging ions or whatever, into the water or is there some sort of chemical reaction in the water which eventually dissipates? How does the coral+ 'wear out' and have to be replaced?
I appreciate ya
Bill

ANSWER:
For freshwater aquariums my experience has been equal to SeaChem (I have had better results with SeaChem products over Kent Marine and use them 10/1 over Kent for marine aquaria). For marine aquariums the Wonder shell help, but the well balanced SeaChem line is hard to beat (such their calcium polyglucanate)
The Large wonder shells are $2.39 and are hard to beat for FW for the price.

My understanding is the same as using a cave chemistry analogy; water containing acids such as carbonic or nitric acid VERY slowly dissolve away the minerals in the crushed coral, etc., which is why that I have found in both freshwater and marine, that the rate of dissolving does not keep up with buffer depletion. Basically the coral does not wear out, but dissolve away.

American Aquarium Products-Aquarium Information