In my 150, I have a tree trunk, a piece of wood that had been in my cichlid tank for quite a while. The piece of wood is held down by a large river rock. The tree trunk came with my 75 I have in the garage.
I also have two pieces of drift wood I got from reputable LFS, this wood doesnt float. Is it possible that this tree trunk may be leaching off hardness that keeps my gh around 10?
Out of all the water changes Iv'e done, I'm sure I have done enough to lower the hardness from 14 to more then just 10.
I have nothing else in the tank that could be maintaining the hardness...unless someone can school me on this
I will limit my answer to the question - "Is it possible that this tree trunk may be leaching off hardness?" - and not extend it to what is causing your tank water hardness to increase.
Wood does have the habit of absorbing chemicals from its surroundings. Any piece of wood which has been retrieved from salt/brackish water; tends to leach salts when placed into non-saline water. Wood which was in very hard or alkaline water will tend to leach salts which increase the hardness or alkalinity of the water into which it has been introduced if the water does not have the hardness or the alkalinity to the level the wood was last in.
Nature always tends to equalise - so the water absorbed by the wood always tends to have the same concentration of salts and chemicals as in the water it is presently in. This means that if the wood has any salt or chemical in its absorbed water which is different from its present water bath then these will leach out - conversely if the water outside the wood has any salt/chemical which is not found in the water absorbed by the wood then these will leach into the wood.