Has anyone ever tested the water from the bottom of one of their overflows on an established tank before?
The reason I ask is I did a water change on a 285 gallon system the night before last, replaced about 30% of the water but got rushed by kids' bedtime at the end. Instead of predissolving the aquarium salt (2/3 cup) I chucked it in the dominant overflow figuring the salt would dissolve and make it's way through the system slowly. Checked the overflow the next morning, salt dissolved so all seemed fine.
Today was the day I decided to move the silver dollars I had growing out in the sump into the main tank. Everything went fine except one of the dollars got spooked and leapt into that overflow. It was in there for a few minutes before I managed to fish it out and put it back in the display tank. Seconds after being back in, it immediately showed signs of osmotic shock (laying sideways on the bottom of the tank, barely but rapidly breathing). I pulled it back to the sump immediately and it seems to be recovering slowly.
I know salt water is more dense than water but figured the flow would slowly spread the salty water throughout the tank. I was wrong. I pulled water from the bottom of that overflow and it showed close to 1.01-1.02 on my ancient hydrometer.
So it turns out there isn't enough flow to move denser water out of the overflow. My worry is that water with dissolved nirate is also more dense than water and I may have two areas of concentrated nirate sitting in my overflows waiting to poison the tank in the case of a large water change that kicks up the water at the bottom of the overflows.
Is this a real concern or am I overthinking it? I'm debating throwing a couple of my sump sponge filters in the overflows or just placing the siphon in the overflows during water changes to see if that changes anything. I'm going to leave the other overflow untouched until I get a new test kit to see if the water there tests different than the display and sump water but wondered if anyone else had done as much.
The reason I ask is I did a water change on a 285 gallon system the night before last, replaced about 30% of the water but got rushed by kids' bedtime at the end. Instead of predissolving the aquarium salt (2/3 cup) I chucked it in the dominant overflow figuring the salt would dissolve and make it's way through the system slowly. Checked the overflow the next morning, salt dissolved so all seemed fine.
Today was the day I decided to move the silver dollars I had growing out in the sump into the main tank. Everything went fine except one of the dollars got spooked and leapt into that overflow. It was in there for a few minutes before I managed to fish it out and put it back in the display tank. Seconds after being back in, it immediately showed signs of osmotic shock (laying sideways on the bottom of the tank, barely but rapidly breathing). I pulled it back to the sump immediately and it seems to be recovering slowly.
I know salt water is more dense than water but figured the flow would slowly spread the salty water throughout the tank. I was wrong. I pulled water from the bottom of that overflow and it showed close to 1.01-1.02 on my ancient hydrometer.
So it turns out there isn't enough flow to move denser water out of the overflow. My worry is that water with dissolved nirate is also more dense than water and I may have two areas of concentrated nirate sitting in my overflows waiting to poison the tank in the case of a large water change that kicks up the water at the bottom of the overflows.
Is this a real concern or am I overthinking it? I'm debating throwing a couple of my sump sponge filters in the overflows or just placing the siphon in the overflows during water changes to see if that changes anything. I'm going to leave the other overflow untouched until I get a new test kit to see if the water there tests different than the display and sump water but wondered if anyone else had done as much.
