Acceptable evaporation before ATO kicks in

epicfatigue · Sep 3, 2023

Hey guys, I redesigned my sump. I miss judged a height.

My tanks total volume is 380L, my ato was supposed to kick in at 250-500ml evaporation. But it now kicks in at 1L-2L mark.

Would this cause to much of a parameter swing ? Alk cal etc

I remember reading something @Randy Holmes-Farley wrote on this once but I can't remember where.

I can make some pretty big adjustments to make this work again but if this is okay be easier to keep as is.

Peace River · Sep 3, 2023

While we wait on a calculation or something more scientific, have you looked at the salinity difference between the low mark and then the high mark after you have added RO to make up the difference?

Gareth elliott · Sep 3, 2023

In a 380L system. 2L evaporation will change salinity from 35ppt to 35.19ppt.

A more dangerous impact will be the localized low salinity during refill while the water homogenizes. Where the ATO is refilling will be be 2L of fresh water till it mixes with the rest of the water.

epicfatigue · Sep 4, 2023

Gareth elliott said:
In a 380L system. 2L evaporation will change salinity from 35ppt to 35.19ppt.

A more dangerous impact will be the localized low salinity during refill while the water homogenizes. Where the ATO is refilling will be be 2L of fresh water till it mixes with the rest of the water.

Yeah I might make it mix in the corner of th sump and put a wavemaker to come on with it.

gbroadbridge · Sep 4, 2023

epicfatigue said:
Hey guys, I redesigned my sump. I miss judged a height.

My tanks total volume is 380L, my ato was supposed to kick in at 250-500ml evaporation. But it now kicks in at 1L-2L mark.

Would this cause to much of a parameter swing ? Alk cal etc

I remember reading something @Randy Holmes-Farley wrote on this once but I can't remember where.

I can make some pretty big adjustments to make this work again but if this is okay be easier to keep as is.

It's not going to make any measurable difference.

o2manyfish · Sep 4, 2023

You're putting too much thought and worry into this issue. The evaporation is slow, and the refilling of your topoff happens over a period of time. Unless you have some amazing topoff that pours 2 liters of water into your sump in the blink of an eye, you got nothing to worry about.

From the photo it looks like you have at least 2 pumps recirculating water thru the sump, plus a skimmer that is circulating water through the sump. Calculate how many liters a minute are passing thru that sump and you will see that in the time it takes for your topoff to cycle the mixing of the freshwater in is not a problem.

And a fresh water blast is not going to cause any issues to corals. I have dove on some amazing reefs that are off the coast in the line of rivers and streams - they get flooded with fresh water and silt and mud and fertilzed and pure crap. And the reefs are thriving.

Dave B

epicfatigue · Sep 4, 2023

o2manyfish said:
You're putting too much thought and worry into this issue. The evaporation is slow, and the refilling of your topoff happens over a period of time. Unless you have some amazing topoff that pours 2 liters of water into your sump in the blink of an eye, you got nothing to worry about.

From the photo it looks like you have at least 2 pumps recirculating water thru the sump, plus a skimmer that is circulating water through the sump. Calculate how many liters a minute are passing thru that sump and you will see that in the time it takes for your topoff to cycle the mixing of the freshwater in is not a problem.

And a fresh water blast is not going to cause any issues to corals. I have dove on some amazing reefs that are off the coast in the line of rivers and streams - they get flooded with fresh water and silt and mud and fertilzed and pure crap. And the reefs are thriving.

Dave B

Awesome thanks mate, I am a massive overthinker, I have had some poor growth issues that I cannot work out and I am just looking at the little things now.