I don't think the lack of dissolved minerals would kill this quickly and consistently unless there was something added to the tank recently that swung the TDS drastically. I think the contamination issue is more from water running along the roof before reaching the pvc.
What are the tap readings? Oftentimes the tap is just fine in terms of water chemistry, just need to be treated with a dechlorinator for chlorine/chloramines.
River rock may only be an issue if they are causing a dramatic change in TDS. Too much aeration is impossible unless the tank becomes super saturated...excess O2 will off gas.
What are the tap readings? Oftentimes the tap is just fine in terms of water chemistry, just need to be treated with a dechlorinator for chlorine/chloramines.
River rock may only be an issue if they are causing a dramatic change in TDS. Too much aeration is impossible unless the tank becomes super saturated...excess O2 will off gas.