Low TDS Tap Water (<40 ppm) - To RO/DI or not?

[OakenGoby]

I kept reef aquariums in the 90s and through the beginning of the 2000s.  I got back into the aquarium hobby with freshwater planted aquariums.  I now have 6: (1) 6 gallon Betta (looking for a new inhabitant - Travis passed after his outing with one of my cats; see other thread); (2) 7 gallon shrimp; (3) 10 gallon community that is now more of a plant grow out tank; (4) 10 gallon shallow shelldwellers; (5) 12 gallon long/shallow Male Endler Fraternity tank with cherry shrimp and some yet-to-be-decided bottom dwellers (Cory cats, Hillstream loaches, Clown Pleco); and (6) 17 gallon cube High energy (high light+CO2) planted tank that is in the design phase - thinking pencilfish, apistos, ember tetras, cardinal tetras, and cory cats.

A holdover from my reefkeeping days is that RO/DI water is essential.  I have a small RO/DI unit that puts out about 50 gpd and returns 0 TDS water.  The membranes are long lasting because of the low TDS of the input water.  I've gone back and forth between using RO/DI and remineralizing or tap and remineralizing (Seachem Tangayika buffer/salt for shellies, SaltyShrimp GH/KH+ for Endlers and Betta, and SaltyShrimp GH+ for Caridina shrimp and the future 17 gallon).  I have not observed any appreciable difference in the health/behavior of the fish and the health of the plants.  This leads me to believe that the extra time/effort to make RO/DI water is not worth it for these aquariums.  Of course when I do use tap, I dechlorinate with a water conditioner (currently Fritz Complete). 

I imagine that most users here use tap water unless their tap is notably poor quality.  Should I get over this mental block and continue to just use tap, or is RO/DI somehow going to really benefit me in the long run?  Thoughts? Feedback? Questions?  I appreciate the help!

OakenGoby

 

[TheSwissAquarist]

On 11/3/2022 at 6:32 PM, OakenGoby said:

I kept reef aquariums in the 90s and through the beginning of the 2000s.  I got back into the aquarium hobby with freshwater planted aquariums.  I now have 6: (1) 6 gallon Betta (looking for a new inhabitant - Travis passed after his outing with one of my cats; see other thread); (2) 7 gallon shrimp; (3) 10 gallon community that is now more of a plant grow out tank; (4) 10 gallon shallow shelldwellers; (5) 12 gallon long/shallow Male Endler Fraternity tank with cherry shrimp and some yet-to-be-decided bottom dwellers (Cory cats, Hillstream loaches, Clown Pleco); and (6) 17 gallon cube High energy (high light+CO2) planted tank that is in the design phase - thinking pencilfish, apistos, ember tetras, cardinal tetras, and cory cats.

A holdover from my reefkeeping days is that RO/DI water is essential.  I have a small RO/DI unit that puts out about 50 gpd and returns 0 TDS water.  The membranes are long lasting because of the low TDS of the input water.  I've gone back and forth between using RO/DI and remineralizing or tap and remineralizing (Seachem Tangayika buffer/salt for shellies, SaltyShrimp GH/KH+ for Endlers and Betta, and SaltyShrimp GH+ for Caridina shrimp and the future 17 gallon).  I have not observed any appreciable difference in the health/behavior of the fish and the health of the plants.  This leads me to believe that the extra time/effort to make RO/DI water is not worth it for these aquariums.  Of course when I do use tap, I dechlorinate with a water conditioner (currently Fritz Complete). 

I imagine that most users here use tap water unless their tap is notably poor quality.  Should I get over this mental block and continue to just use tap, or is RO/DI somehow going to really benefit me in the long run?  Thoughts? Feedback? Questions?  I appreciate the help!

OakenGoby

 

Just use tap(, unless you're like me and your pH is 8.6)!

I've been using rainwater (free RO water) and I can't attribute any set backs to it.

Any pics of the tanks ??

[OakenGoby]

[meadeam]

I never thought I'd be interested in "making" water, but I'm starting down that path.  My fish are doing great without it, it's just more a desire on my part to get closer to whatever version of perfect I have in my head.  It is a hobby after all, so we embrace the parts of it that we enjoy doing.  If that means constructing water, then that's fine.  The only exception would be if you were keeping fish that just can't thrive at all in your tap water which doesn't seem to be the case.

 

[AllFishNoBrakes]

To me, with your tap being near R/O already, it just seems like an extra wasted step. If your livestock are thriving why change it? I’m a big fan of “if it’s not broken don’t fix it”. 

[OakenGoby]

I'm doing the bulk of the work already, which is making sure I have the correct minerals depending on the species kept.  The base water is either tap at 40 TDS or RO/DI at 0 TDS.  Any trace amounts of metal are eliminated by the water conditioner and any chlorine is neutralized, so with the tap I'm left with just a little more TDS in the finished water versus the RO/DI.  It's honestly not that difficult to make water, but with my current setup I do need to baby sit to ensure no overflow.  I'm not sure I'm going to find the answer posting here, but I think there's plenty of evidence that using tap is sustainable for most people and their fish.  

On 11/3/2022 at 3:20 PM, AllFishNoBrakes said:

To me, with your tap being near R/O already, it just seems like an extra wasted step. If your livestock are thriving why change it? I’m a big fan of “if it’s not broken don’t fix it”. 

I'm not sure I can tell if it's 100% not broke since I've kind of gone back and forth.  Having the RO/DI system in place definitely makes me feel like I should be using it.  Whether or not I need to use it is another story...but I'm leaning towards no. 

[redfish]

On 11/3/2022 at 3:20 PM, OakenGoby said:

 I'm not sure I'm going to find the answer posting here, but I think there's plenty of evidence that using tap is sustainable for most people and their fish.  

I'm not sure I can tell if it's 100% not broke since I've kind of gone back and forth.  Having the RO/DI system in place definitely makes me feel like I should be using it.  Whether or not I need to use it is another story...but I'm leaning towards no. 

Sounds like you need to do a side by side test if you really want gain more insight into your question based on your water conditions.

[OakenGoby]

On 11/3/2022 at 5:19 PM, redfish said:

Sounds like you need to do a side by side test if you really want gain more insight into your question based on your water conditions.

I was just thinking this. Going to play chemist this weekend. Draw a cup of both and use the Aquarium Co-Op strips to see where we stand. 

[AllFishNoBrakes]

By all means, if you wanna play with your toys then play away! Just being so close to 0 already if feels like, to me, the saltwater ways are creeping back in. Who am I to judge your hobby, though?
 

For me, I’d rather just work with what I have. In CO, we have soft water, and I simply don’t want to “make” water to try to keep things that wouldn’t naturally thrive in what I have. When I first got into the hobby, I was adamant I wanted a reef tank. Then, I realized I didn’t want to make and store water, spend a bunch on lights for corals, have to target feed corals, etc. With as much as I already work for my real job that pays for everything else, I want my hobby to be as easy as possible. Change water weekly, squeeze a filter every once in a while, add fertilizer, raise the fry from the fish that breed for me, but mostly sit back and enjoy. 

[Andy's Fish Den]

I would love to have your water for my tap water. I have hard well water, usually tests around 300 TDS 7.8-8.2 pH. I would just use tap, and if you're itching to put that RO/DI unit to work, use it to get the 0TDS water to remineralize for the caridina shrimp. 

[OakenGoby]

Here’s the test results. Water-in TDS 29 ppm, water-out TDS 0 ppm. Aquarium Co-op strips return identical results. Conclusion - negligible difference. 
 

tap on left, RO/DI right 

[anewbie]

Depends on fish species; for the ones pictured 29 is fine - almost too soft for those shrimps; but for some true blackwater fishes you might feel better with ro/di.

I think some of the more exotic species of betta also prefer near blackwater conditions (blackwater is NOT about tannis; it is about ultra low conductivity/purity of the water).

Edited November 4, 2022 by anewbie

[OakenGoby]

On 11/4/2022 at 3:35 PM, anewbie said:

Depends on fish species; for the ones pictured 29 is fine - almost too soft for those shrimps; but for some true blackwater fishes you might feel better with ro/di.

I think some of the more exotic species of betta also prefer near blackwater conditions (blackwater is NOT about tannis; it is about ultra low conductivity/purity of the water).

Regardless of the base water I’m remineralizing. Since the difference is negligible, it seems silly to use RO/DI then remineralize. 

[anewbie]

On 11/4/2022 at 2:42 PM, OakenGoby said:

Regardless of the base water I’m remineralizing. Since the difference is negligible, it seems silly to use RO/DI then remineralize. 

Well one other thing to consider is exactly what that 40tds is composed of ....

[OakenGoby]

Well, I figured I'd rather be safe than sorry.  I'm 100% sure what's coming out of the RO/DI unit, so I'll stick with that.