Hello, this be my first post although I have been a long time lurker. This is a great forum and I do wish my first post was not to ask for help but I am in quandry....
See, I thought I'd help out a friend by rebuilding his shallow water garden. Its 16' x 6' x 2 ' deep, total about 1000 gallons. I intended to put in a reverse flow undergravel filter where there is a framework across the entire pond floor which is covered in gravel. A pump then pushes water up throug the gravel thereby providing some bio filtration. It's not a real koi pond as such but he's happy with it.
So I made the frame out of Kapur (tropical) wood. Remember, this frame supports the gravel so I used a fair amount of wood. So after the first fill up, the water turned brown. The wood leaches out some resins or such. Ph also was low, about 5. I was expecting this. After a week of water changes and overflows, the water was clearish again with just a tinge of brown. With oyster shells, the Ph was 7 and steady.
So I put in some feeder fish to test. They were dead by the next day! Not only that but they stank to high heaven! There was a faint but distinct smell of decay from the pond water. I really don't know what to make of this. Could the Kapur wood be leaching toxins into the water? What kind of toxin would cause the dead fish to stink so much? The dead fish looked alright (a part from being dead), no obvious signs of decomposition but they sure stank.
So today, did a full water change and added dechlor. Also put in a kilo of activated carbon right at the pump. Put some more feeder fish in. Am waiting for results tomorrow.
Also, there is a sandstone fountain type thing in the pond. Could that be an issue? I'm thinking not.
Any ideas would be most appreciated. My friend is not impressed and I am embarassed. I have used this wood before in my pond but never in such large amounts.