Constant Top Off effect on Nitrates

kesh · Sep 12, 2017

Hi, i have a 30 gallon open top fowler which regularly requires around 3 gallons of top off weekly from evaporation. I was wondering since im topping off almost 10% weekly, do i still need water change to reduce nitrates. For instance, salt level increase with evaporation. But im assuming nitrate ecaporates with water that evaporates. So topping off level is constantly reducing the levels similar to water change. Makes sense?

Antics · Sep 12, 2017

Nitrates aren't leaving the water due to evaporation. You will still need to utilize some form of nutrient export via water changes, skimmer, chemical filtration, etc.

kesh · Sep 12, 2017

Antics said:
Nitrates aren't leaving the water due to evaporation. You will still need to utilize some form of nutrient export via water changes, skimmer, chemical filtration, etc.

May i know your source for this (ie test done with nitrate kits or scientific reasoning). My humble logic is if all the water evaporates, you dont see any nitrates residue, unlike salt. So, nitrates dissolved in the water that evaporates, evaporates too?

Antics · Sep 12, 2017

According to the National Ground Water Association they do not.

oscargrumete61 · Sep 12, 2017

kesh said:
May i know your source for this (ie test done with nitrate kits or scientific reasoning). My humble logic is if all the water evaporates, you dont see any nitrates residue, unlike salt. So, nitrates dissolved in the water that evaporates, evaporates too?

If you think you are right do not make any
Water changed and see your aquarium works and if its fine keep that way

kesh · Sep 12, 2017

oscargrumete61 said:
If you think you are right do not make any
Water changed and see your aquarium works and if its fine keep that way

Of coz i dont think im right, its a logical opinion i have and hence the question. Asking for Antics reasons is to know where's he coming from. If i think im right, i would have done it without asking. LOL. If you have nothing informative to contribute, pls dont.

oscargrumete61 · Sep 12, 2017

kesh said:
Of coz i dont think im right, its a logical opinion i have and hence the question. Asking for Antics reasons is to know where's he coming from. If i think im right, i would have done it without asking. LOL. If you have nothing informative to contribute, pls dont.

I have nothing informative because you were not asking you were telling us what you are gonna do

DSC reef · Sep 12, 2017

Never heard of nitrates evaporating. I agree with antics. Plus, it sounds like he gave a pretty good source as well.

kesh · Sep 12, 2017

oscargrumete61 said:
I have nothing informative because you were not asking you were telling us what you are gonna do

When exactly did i do that? Pls read again. I said, do i still need water changes to reduce nitrates? I didn't state, i don't need to do water change. Also note the multiple question marks.

Antics · Sep 12, 2017

Hey Kesh,

My degree is in Geology and a lot of my focus in university had to so with groundwater and aquifers so take what I'm saying with a grain of salt in relation to saltwater and aquariums.

Nitrates are not going to leave your aquarium in any meaningful way via evaporation. I'd love to give more info but my power is out from a hurricane so I'm trying to keep my answer brief for you and referenced the National Ground Water Association above if you want to take a look at how nitrates (commonly found in fertilizers) make it into surface and groundwater which is of course a contaminant. Evaporation is not a solution for removing them. Water changes and or chemical filtration are best. Carbon dosing is also very popular.

kesh · Sep 12, 2017

Antics said:
Hey Kesh,

My degree is in Geology and a lot of my focus in university had to so with groundwater and aquifers so take what I'm saying with a grain of salt in relation to saltwater and aquariums.

Nitrates are not going to leave your aquarium in any meaningful way via evaporation. I'd love to give more info but my power is out from a hurricane so I'm trying to keep my answer brief for you and referenced the National Ground Water Association above if you want to take a look at how nitrates (commonly found in fertilizers) make it into surface and groundwater which is of course a contaminant. Evaporation is not a solution for removing them. Water changes and or chemical filtration are best. Carbon dosing is also very popular.

Thank you. I appreciate the knowledge.

Velcro · Sep 12, 2017

The short answer is: No, nitrate absolutely is NOT leaving the tank as water evaporates.

The long answer is:

The only thing that evaporates from your aquarium is water (H2O). Everything else stays behind, and actually becomes more concentrated unless you top off, which you do.

The only way nitrogen is going to leave the tank (other than water changes) is if it part of algae that you are removing, or if you have very good nitrifying bacteria which converts the NO3 to N2 (nitrogen gas) which will leave the water (assuming the concentration of nitrogen gas in the air around the aquarium is lower than the nitrogen gas in the tank).

Randy Holmes-Farley · Sep 12, 2017

kesh said:
May i know your source for this (ie test done with nitrate kits or scientific reasoning). My humble logic is if all the water evaporates, you dont see any nitrates residue, unlike salt. So, nitrates dissolved in the water that evaporates, evaporates too?

No, there is no ion (a charged molecule) that evaporates, and nitrate is an ion. No evaporation at all.

BlueCursor · Sep 13, 2017

Op, think of it this way. If "stuff" besides water evaporated, then your salt would evaporate and you would use salt water to top off, not RO water. Since you only replace pure water, that must be all that is evaporating.

Gino · Sep 15, 2017

I'm not an expert for shure, but with the evaporated water your concentration of nitrate will increase because is less diluted. As soon you pour fresh water you will see a reduction on your readings because it's a little diluted, but the nitrate still in. The only way to exports nitrate is by water changes and some others nitrate exports methods. As far as I know oxigen is the other element that been depleted with the evaporation process. But that's is something, that is almost undetectable because of the water movement, and the protein skimmers adding air constantly.

S-t-r-e-t-c-h · Sep 15, 2017

Antics said:
According to the National Ground Water Association they do not.

Here's the one-pager from the NGWA:

http://www.ngwa.org/Documents/ClipCopy/Nitrates.pdf

Will boiling water get rid of nitrates or lower nitrate levels to a safe amount?
No, because nitrates don’t evaporate. In fact, boiling will increase the concentration of nitrates in water.

Randy Holmes-Farley · Sep 15, 2017

Gino said:
As far as I know oxigen is the other element that been depleted with the evaporation process. But that's is something, that is almost undetectable because of the water movement, and the protein skimmers adding air constantly.

There is a huge flux of many gases (N2, O2, CO2, H2O, Ar, He, Ne, even NH3 and H2S, as well as many organic molecules such as dimethylsulfide, one of the "smells of the ocean") in both directions at the air/water surface, and the relative amounts on each side (that is, the concentrations in the air and in the water) is what determines whether there is net entry or exit of that material from the water.