Uberhoust
Fish Herder
SDg are granites which is not the rocks you have.
The other, Sy, is quite an interesting mix with turbidic rocks, rocks formed from sediments that have flowed, mixed and partially sorted after their initial deposition in the water. Could fit with the rocks you have, dirty sandstone looking.
Duw is mostly rhyolite, this is an acidic fine grained rock, the quicker cooling equivalent of granite. I have had rhyolite in my tanks without any noticeable change in pH or GH. Rhyolite can vary a lot in color but your rocks do not look like any rhyolite I have seen or collected.
Given the information currently available I would suggest you have a dirty sandstone/mudstone mix with a lot of incorporated organic material entrapped within the rock. The main color of the rock is not red but grayish with red staining suggesting that the sediments were in an anerobic environment and were not strongly oxidized, and there is iron present in the sediments. There is a possibility that the oxidization of the iron and the organic material within the rock can release acids into the water. Additionally mudstone in particular does not make for good rocks to use in water because they are made of clay minerals that readily absorb water, unfortunately they expand when they absorb water and can tend to break down unless cemented with calcium carbonate, or silica minerals. The breakdown of the rocks would expose more of the surface of the rock to react with the water. Without a significant acid reaction we know there is not significant calcium carbonate within the rock. The rocks would have the potential to drive up the acidity of the water. They would also be more variable than a lot of other rock types due to how they were deposited.
FYI I am not a geologist, just someone who has a very strong interest in the subject. I am making a lot of assumptions here based on a small amount of information.
The other, Sy, is quite an interesting mix with turbidic rocks, rocks formed from sediments that have flowed, mixed and partially sorted after their initial deposition in the water. Could fit with the rocks you have, dirty sandstone looking.
Duw is mostly rhyolite, this is an acidic fine grained rock, the quicker cooling equivalent of granite. I have had rhyolite in my tanks without any noticeable change in pH or GH. Rhyolite can vary a lot in color but your rocks do not look like any rhyolite I have seen or collected.
Given the information currently available I would suggest you have a dirty sandstone/mudstone mix with a lot of incorporated organic material entrapped within the rock. The main color of the rock is not red but grayish with red staining suggesting that the sediments were in an anerobic environment and were not strongly oxidized, and there is iron present in the sediments. There is a possibility that the oxidization of the iron and the organic material within the rock can release acids into the water. Additionally mudstone in particular does not make for good rocks to use in water because they are made of clay minerals that readily absorb water, unfortunately they expand when they absorb water and can tend to break down unless cemented with calcium carbonate, or silica minerals. The breakdown of the rocks would expose more of the surface of the rock to react with the water. Without a significant acid reaction we know there is not significant calcium carbonate within the rock. The rocks would have the potential to drive up the acidity of the water. They would also be more variable than a lot of other rock types due to how they were deposited.
FYI I am not a geologist, just someone who has a very strong interest in the subject. I am making a lot of assumptions here based on a small amount of information.
