Water Change - Evaporation

kjaye21 · 02/06/2015, 11:37 AM

Hello all,

I hope this isn't a stupid question but I have never had to think about this previously as I have had glass lids on my tanks before.. however now I have an open top system. My question is.. every two days or so I am replacing about 1 gallon of water in my tank due to evaporation. So roughly 2-3 gallons per week. So if i'm doing a 25% water change should I take into consideration the amount I have replaced with evaporation? To me that is kind of like I just changed those 2-3 gallons per week. I hope that makes sense..thanks!

gone fishin · 02/06/2015, 11:41 AM

The water you are replacing is freshwater,the salt does not evaporate. When you do your WC just figure what you normally do whatever that is. Good luck

coffee_snob · 02/06/2015, 11:48 AM

No.

The "bad stuff" water change gets rid of does not evaporate with the water, so don't figure evaporation with water change amount.

I lose 5+ gallons per week due to evaporation, and still do 10% water change per week.

FraggledRock · 02/06/2015, 11:57 AM

make sure you "top off" with fresh RODI water.

don't compound top offs with salt, or you will keep adding salt and raising your salinity

tmz · 02/06/2015, 12:27 PM

The good stuff added with water changes doesn't evaporate either.
Fresh ro/di handles evaporation.
There might be some small amount of salinity lost to mist ,salt creep and skimmate though;so checking the tank's salinity from time to time is prudent as it may need a little salt water top off from time to time to remain constant.

Sk8r · 02/06/2015, 12:42 PM

Only H's and O's evaporate [H2O]---and minerals stay behind. Your salt mix (read the label) contains a chemist's workshop of elements. Depending on the species you keep, they will use some of those elements up faster than your water changes can replace them. Corals using calcium and a wee bit of magnesium are the major example---which means for stony coral you ultimately have to add more of both (putting kalk powder in your topoff bucket handles the calcium, and mag supplement is equally easy)---BUT tank water does get out of balance, which can screw things up. Test your alkalinity once weekly and if it is around 8.3, that's good. If it's falling, you will need to dose with buffer. The minor elements aren't going to be a problem---our water changes are enough to keep those available. But buffer is something that has to be watched---not just by coral-keepers, but by everybody. A jar of buffer is a must, and an alkalinity test will tell you how much to put in to keep it steady. If your tank WILL NOT keep the alk up, it is telling you you are low in magnesium and your water changes are not doing the trick: at that point you dose magnesium (should be about 1300) and probably calcium (should be about 420). You always wait 12 hours to re-test to see how the dose worked. HTH.

kjaye21 · 02/06/2015, 01:37 PM

Ahh Ok, the answer about the bad stuff not evaporating is my answer.. thanks for chiming in. I do my regular water changes but I was just curious about the evaporation since I never really had to deal with it before. Thanks guys!

skeeter_ca · 02/06/2015, 01:52 PM

Before you do your water change top off your DT with fresh RO/DI water and check salinity of the DT then match your water change water to the tank before adding.

skeeter

Mishri · 02/06/2015, 03:14 PM

Yes, good point skeeter, before a water change your water level should be full, otherwise if you fill it each time with fresh salt water your salinity will rise up. You might want to check it now and make sure it isn't too high if you haven't been using top off water. Even with glass lids I still get about 5 gallons of evaporation over 2 weeks on my 75 gallon (better to keep on top of it so it doesn't get that bad, add daily if needed)

tmz · 02/06/2015, 04:29 PM

bad stuff not evaporating is my answer.

While water changes do export some organics ,inorganic nutrients and other elements;they also provide major minor and trace elements in useful proportions which IMO is a more important reason to do them.
Nutrients can be controlled with a variety of filtration and removal methods and will often build right back up after water changes if the balance between inputs mostly from food and export via mechanical and biological filtration and removal are left imbalanced.

02/06/2015, 11:37 AM	#1
kjaye21 Registered Member Join Date: Oct 2014 Posts: 8	Water Change - Evaporation Hello all, I hope this isn't a stupid question but I have never had to think about this previously as I have had glass lids on my tanks before.. however now I have an open top system. My question is.. every two days or so I am replacing about 1 gallon of water in my tank due to evaporation. So roughly 2-3 gallons per week. So if i'm doing a 25% water change should I take into consideration the amount I have replaced with evaporation? To me that is kind of like I just changed those 2-3 gallons per week. I hope that makes sense..thanks!

02/06/2015, 11:41 AM	#2
gone fishin Registered Member Join Date: Jul 2011 Location: Wyocena Wi Posts: 6,936	The water you are replacing is freshwater,the salt does not evaporate. When you do your WC just figure what you normally do whatever that is. Good luck __________________ Tony Current Tank Info: 180gal DT, BM NAC77 skimmer,3 Maxspect razors, Maxspect Gyre 150, 30g QT

02/06/2015, 11:48 AM	#3
coffee_snob Registered Member Join Date: Dec 2014 Location: Grand Rapids, MI Posts: 296	No. The "bad stuff" water change gets rid of does not evaporate with the water, so don't figure evaporation with water change amount. I lose 5+ gallons per week due to evaporation, and still do 10% water change per week. __________________ Webcam: http://myreeftank.weebly.com/

02/06/2015, 11:57 AM	#4
FraggledRock Registered Member Join Date: Dec 2014 Location: New York, New York Posts: 2,185	make sure you "top off" with fresh RODI water. don't compound top offs with salt, or you will keep adding salt and raising your salinity __________________ “For most of history, man has had to fight nature to survive; in this century he is beginning to realize that, in order to survive, he must protect it.”― Jacques-Yves Cousteau MarineBio.org Current Tank Info: 40 Gallon Breeder w/ Bean Animal Overflow 20G Sump, Mixed Reef.

02/06/2015, 12:27 PM	#5
tmz ReefKeeping Mag staff Join Date: Apr 2006 Location: West Seneca NY Posts: 27,691	The good stuff added with water changes doesn't evaporate either. Fresh ro/di handles evaporation. There might be some small amount of salinity lost to mist ,salt creep and skimmate though;so checking the tank's salinity from time to time is prudent as it may need a little salt water top off from time to time to remain constant. __________________ Tom Current Tank Info: Tank of the Month , November 2011 : 600gal integrated system: 3 display tanks (120 g, 90g, 89g),several frag/grow out tanks, macroalgae refugia, cryptic zones. 40+ fish, seahorses, sps,lps,leathers, zoanthidae and non photosynthetic corals.

02/06/2015, 12:42 PM	#6
Sk8r RC Mod Join Date: Feb 2006 Location: Spokane WA Posts: 34,628 Blog Entries: 55	Only H's and O's evaporate [H2O]---and minerals stay behind. Your salt mix (read the label) contains a chemist's workshop of elements. Depending on the species you keep, they will use some of those elements up faster than your water changes can replace them. Corals using calcium and a wee bit of magnesium are the major example---which means for stony coral you ultimately have to add more of both (putting kalk powder in your topoff bucket handles the calcium, and mag supplement is equally easy)---BUT tank water does get out of balance, which can screw things up. Test your alkalinity once weekly and if it is around 8.3, that's good. If it's falling, you will need to dose with buffer. The minor elements aren't going to be a problem---our water changes are enough to keep those available. But buffer is something that has to be watched---not just by coral-keepers, but by everybody. A jar of buffer is a must, and an alkalinity test will tell you how much to put in to keep it steady. If your tank WILL NOT keep the alk up, it is telling you you are low in magnesium and your water changes are not doing the trick: at that point you dose magnesium (should be about 1300) and probably calcium (should be about 420). You always wait 12 hours to re-test to see how the dose worked. HTH. __________________ Sk8r Salinity 1.024-6; alkalinity 8.3-9.3 on KH scale; calcium 420; magnesium 1300, temp 78-80, nitrate .2. Ammonia 0. No filters: lps tank. Alk and cal won't rise if mg is low. Current Tank Info: 105g AquaVim wedge, yellow tang, sailfin blenny,royal gramma, ocellaris clown pair, yellow watchman, 100 microceriths, 25 tiny hermits, a 4" conch, 1" nassarius, recovering from 2 year hiatus with daily water change of 10%.

02/06/2015, 01:37 PM	#7
kjaye21 Registered Member Join Date: Oct 2014 Posts: 8	Ahh Ok, the answer about the bad stuff not evaporating is my answer.. thanks for chiming in. I do my regular water changes but I was just curious about the evaporation since I never really had to deal with it before. Thanks guys!

02/06/2015, 01:52 PM	#8
skeeter_ca Registered Member Join Date: Dec 2003 Location: Yucaipa, CA Posts: 1,007	Before you do your water change top off your DT with fresh RO/DI water and check salinity of the DT then match your water change water to the tank before adding. skeeter __________________ skeeter - It is easier to ask for forgiveness than premission. My motto to my wife. Current Tank Info: 75rr,6"dsb,refugium,auto top-off & semi-auto water changer, OM squirt. 4 MJs 1200, Started on 03/03/06

02/06/2015, 03:14 PM	#9
Mishri Registered Member Join Date: Jul 2004 Location: Great Falls, MT Posts: 1,404	Yes, good point skeeter, before a water change your water level should be full, otherwise if you fill it each time with fresh salt water your salinity will rise up. You might want to check it now and make sure it isn't too high if you haven't been using top off water. Even with glass lids I still get about 5 gallons of evaporation over 2 weeks on my 75 gallon (better to keep on top of it so it doesn't get that bad, add daily if needed)

02/06/2015, 04:29 PM	#10
tmz ReefKeeping Mag staff Join Date: Apr 2006 Location: West Seneca NY Posts: 27,691	bad stuff not evaporating is my answer. While water changes do export some organics ,inorganic nutrients and other elements;they also provide major minor and trace elements in useful proportions which IMO is a more important reason to do them. Nutrients can be controlled with a variety of filtration and removal methods and will often build right back up after water changes if the balance between inputs mostly from food and export via mechanical and biological filtration and removal are left imbalanced. __________________ Tom Current Tank Info: Tank of the Month , November 2011 : 600gal integrated system: 3 display tanks (120 g, 90g, 89g),several frag/grow out tanks, macroalgae refugia, cryptic zones. 40+ fish, seahorses, sps,lps,leathers, zoanthidae and non photosynthetic corals.