RO/DI water for top off

[sommer08]

I've been struggling a lot with my water parameters lately, so I finally broke down and bought a ro/di unit to make my own water instead of buying it from my LFS. I'm pretty comfortable with making my own salt mix, but I'm confused about top off. Do I have to do anything to my water after it's made before I use it to top off? I've seen some things about remineralizing and ph adjustment so I'm not sure.

 

[JustinTanks]

I’ve never had issues with using RODI water for top offs. I just check it with a TDS meter then add it to my ATO resevoir.

 

[ying yang]

For freshwater tanks say if have fish that need higher ph like some cichlids then when use rodi water which strips most things out then its wise to add minerals back and ph buffers and the like but my top off water ( rodi water with 0 tds) i add nothing to it.
The salt mixes we use have all the major and minor elements we need so no i wouldnt be adding anything in your rodi water for evaporated top off water as when saltwater in our tanks evaporates with the heat/surface agitation and the likes only freahwater evaporates and the salt and the likes stays in tank so only plain old rodi water needs be used for top off.

Some add some kind of supplements as a form of dosing to get added with the top off water but thats a whole different story.

Edit : i know this a reef site but feel i need to add when i mentioned cichlid tanks and adding minerals and ph buffers to rodi i was meaning the water in general and not saying add minerals and buffers for top off water for them tanks incase someone thought i was saying that as messaging and reading things can get mis-interperated very easily ^_^

 

[sommer08]

For freshwater tanks say if have fish that need higher ph like some cichlids then when use rodi water which strips most things out then its wise to add minerals back and ph buffers and the like but my top off water ( rodi water with 0 tds) i add nothing to it.
The salt mixes we use have all the major and minor elements we need so no i wouldnt be adding anything in your rodi water for evaporated top off water as when saltwater in our tanks evaporates with the heat/surface agitation and the likes only freahwater evaporates and the salt and the likes stays in tank so only plain old rodi water needs be used for top off.

Some add some kind of supplements as a form of dosing to get added with the top off water but thats a whole different story.

Edit : i know this a reef site but feel i need to add when i mentioned cichlid tanks and adding minerals and ph buffers to rodi i was meaning the water in general and not saying add minerals and buffers for top off water for them tanks incase someone thought i was saying that as messaging and reading things can get mis-interperated very easily ^_^

Thanks! This is kind of what I was thinking. I do also have a cichlid tank, so it's worth having the extra knowledge as well. I wasn't planning on using ro/di for my fresh tanks yet but I'm sure I'll eventually go down that path.

 

[dbowman5]

the point of topping off your tank is to replace evaporation losses. when salt water evaporates only H2O evaporates. all of the salt and minerals remain in the tank. when salt water splashes out the water evaporates leaving the dissolved stuff on the outside of the tank liquid, so you develop deposits we call salt creep, crystalized minerals. when you remove liquid with a skimmer that is everything that is in the tank, heavy on proteins and insoluble materials. when your losses include salt you need to replace the lost volume with salt water mix. you will know which you should do based on the salinity/ specific gravity results.

 

[Fellowfishy]

Why do we only use RoDi water to topoff instead of saltwater? I forgot. I am new here and have a nano tank with a clown and a banded shrimp. Who keeps molting every 2-3 weeks and his antennas are getting too big. I'm bummed he may out grow my tank! I've only had it since July 2024.
* Oops never-mind. Just read dbowman5 post.

 

[Randy Holmes-Farley Verified Community Expert]

Why do we only use RoDi water to topoff instead of saltwater? I forgot. I am new here and have a nano tank with a clown and a banded shrimp. Who keeps molting every 2-3 weeks and his antennas are getting too big. I'm bummed he may out grow my tank! I've only had it since July 2024.
* Oops never-mind. Just read dbowman5 post.

The salt does not evaporate but the pure water does.
Thus, you need to add back pure water and not salt.