How incoming water mixes

[Jeremy165]

I have a 125 gallon display tank with a 30 gallon sump. I don’t have ATO.

Sometimes I’ll go to do my weekly tank cleaning and water change and notice that the water level in my sump is low. If I removed water for a water change from my DT, the water level would become too low in my sump and my return pump would start sucking air. So before I remove water from the tank, I’ll add 4 or 5 gallons of RO/DI water to the sump to bring the water level up.

My thinking is that if I then removed water from the DT, I’d be removing mainly the new RO/DI water. I wouldn’t be removing nutrient-rich water, which is the goal of the water change.

To avoid that, how long would you wait to make sure that the RO/DI water has mixed thoroughly with the tank and sump water before removing water from the DT?

Or am I overthinking things, and in the grand scale, 4-5 gallons of water would mix in pretty quickly with the approx. 150 gallons of combined tank and sump water?

Thanks!

 

[TX_REEF]

I think you're over-thinking it, but I would strongly recommend an ATO, it's super affordable versus time and effort saved

I use this unit on all my systems and it works great: https://amzn.to/44Urq1P

 

[Mr Fishface]

I would think a few minutes enough time for it to mix. But maybe others will have other opinions! I also strongly recommend an ATO if you have room for one. When I had my 125 with a sump it was my favorite upgrade by far.

 

[Randy Holmes-Farley Verified Community Expert]

An automatic water change system can add water slowly and return it simultaneously, and if set up right, you do not take out any unmixed in clean water.

If you go manual, maybe turn off the return pump during the water change. Then you can remove what you want, and add clean water.

 

[foamboy]

You should be topping off more frequently or with ATO to keep salinity in check. And as far as water changes go, I shut my sump off during them.

 

[KStatefan]

I have a 125 gallon display tank with a 30 gallon sump. I don’t have ATO.

Sometimes I’ll go to do my weekly tank cleaning and water change and notice that the water level in my sump is low. If I removed water for a water change from my DT, the water level would become too low in my sump and my return pump would start sucking air. So before I remove water from the tank, I’ll add 4 or 5 gallons of RO/DI water to the sump to bring the water level up.

Get an ATO

If you are removing salt water you need to replace it with saltwater.

 

[Jeremy165]

Get an ATO

If you are removing salt water you need to replace it with saltwater.

I like not having ATO as it keeps me very hands-on and aware of whats going on in my tank.

I of course replace evaporation with freshwater, and when I do a water change from my tank replace that water with a fresh batch of saltwater.

 

[KStatefan]

I like not having ATO as it keeps me very hands-on and aware of whats going on in my tank.

I of course replace evaporation with freshwater, and when I do a water change from my tank replace that water with a fresh batch of saltwater.

OK

This "before I remove water from the tank, I’ll add 4 or 5 gallons of RO/DI water to the sump to bring the water level" made it sound like you were adding RODI water then removing tank water.

 

[Jeremy165]

OK

This "before I remove water from the tank, I’ll add 4 or 5 gallons of RO/DI water to the sump to bring the water level" made it sound like you were adding RODI water then removing tank water.

I'd be adding RODI water to combat evaporation. Then let that water mix with all the water in the display tank. Then remove saltwater as part of the water change, then replace that saltwater as part of the water change.

The main question was, after adding the RODI water, how long would it take for that new RODI water to mix with all the water in the tank so that all the water in the tank was homogeneous?