Is RO filter wasting water? - The Planted Tank Forum
LinkBack Thread Tools Display Modes
post #1 of 4 (permalink) Old 03-25-2016, 08:10 PM Thread Starter
Wannabe Guru
Edward's Avatar
PTrader: (0/0%)
Join Date: Apr 2005
Location: at home
Posts: 1,358
Is RO filter wasting water?

RO filters are not wasting water when used with aquariums.
Here is an example of cleaning up 400L aquarium from 600 S to 340 S with tap versus RO.

With 330 S tap
30% WC, 600 -> 510 (- 90)
30% WC, 510 -> 450 (- 60)
30% WC, 450 -> 410 (- 40)
30% WC, 410 -> 383 (- 27)
30% WC, 383 -> 365 (- 18)
30% WC, 365 -> 353 (- 12)
30% WC, 353 -> 345 (- 8)
30% WC, 345 -> 340 (- 5)
Total amount of used water ≈ 1000 L

With 10 S RO
30% WC, 600 -> 403 (- 197)
16% WC, 403 -> 340 (- 63)
Amount of used RO clean water ≈ 200 L
Amount of used RO waste water ≈ 800 L at 1 : 4 drain ratio
Total amount of used water ≈ 1000 L

Cleaning up aquariums properly with tap and RO uses the same amount of raw water.

Thank you

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Edward is offline  
Sponsored Links
post #2 of 4 (permalink) Old 03-25-2016, 11:56 PM
Planted Tank Guru
PTrader: (0/0%)
Join Date: Jan 2010
Location: Contra Costa CA
Posts: 11,721
The slower process, using 8 water changes is easier on the fish.
If you did 2 of these water changes per week for a month the fish would have a month to get used to the lower TDS. Even the most sensitive fish can handle this slow change.

The faster process, using just 2 water changes is too fast for the fish. They need more time to adjust their metabolism to the greatly reduced TDS.
If you use RO water to do this, do much smaller water changes and let the process take time.
Diana is offline  
post #3 of 4 (permalink) Old 03-26-2016, 12:22 AM Thread Starter
Wannabe Guru
Edward's Avatar
PTrader: (0/0%)
Join Date: Apr 2005
Location: at home
Posts: 1,358
Hi Diana
How hard would it be on fish when being moved from 6 to 4 dGH?

Thank you

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Edward is offline  
post #4 of 4 (permalink) Old 03-26-2016, 02:10 AM
Wannabe Guru
dukydaf's Avatar
PTrader: (0/0%)
Join Date: Dec 2004
Location: Rome
Posts: 1,273
In my experience, most fish are not overly stressed by the proposed change of 2 dGH in the aquarium water. It is still gradual when we change the water in our aquariums. Think of it as the weekly flash flood . I find it more problematic when people dunk fish in another aquarium with different water parameters without providing time for fish to adapt to the new water ( stress also from moving + new aquarium). However there are other things in the water that influence the osmotic pressure that are not measured by the General Hardness.

The bigger thing here is why would one aim at a specific conductivity/TDS when growing plants ???

Will plants die at 410 S and blossom at 310 S ? What is the impact on the plants between changing your water with tap ( say NO3=0, PO4=0, GH=10, KH=8, high conductivity) and (remineralized) RO (NO3=0, PO4=0, GH=3, KH=1, low conductivity) ? I say remineralized as under normal conditions you will run into Mg deficiency pretty fast if using pure RO. Bottom line, it is not the conductivity that matters, it is what makes it high.

I've grown plants using both hard tap water and remineralized RO. Very different values in conductivity, mainly due to different values in GH and KH. In both cases I would notice a small increase during the week due to EI fertilizing, evaporation, by-products. It would revert to standard value with the 50% WC. Difference in most plants was minimal, just needed to adjust my CO2.

Now, some shrimps and fish do require very soft water, and are sensitive to this issue. RO water will therefore be needed from the start . However, the shrimps/fish will respond in different ways if the conductivity increased due to KH/GH increase or due to nitrates build-up or other factors. How sensitive are CRS to an increase in conductivity when KH was kept low I have yet to determine but my guess is that the real problems come from increased KH/GH.

On hiatus till later this year
dukydaf is offline  


Quick Reply

Register Now

In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome