Ro Water

[kirkster]

Hi all, I thought I'd start a new thread on this as it was getting tangled up with my Algae thread.
 
I have filled my new 90G tank (currently in fishless cycling) with RO water more out of the fact that I have always been doing this with my 20G.  However, with my much bigger tank this could get expensive and totally impractical if doing large water changes that some seem to suggest is a good practise.  Transporting 150kg  (over 300lb to you US guys) which equates to half the tank for a 50% change is not exactly a simple proposition!
 
LFS where I get the RO from is just down the road and is in the same water company municipality on their hardness charts.  Th PH of tap water is 8.0 and the GH is 8.3.  The Ph of the RO is hardly any different but I cannot comment on the GH of it...  All my Ammonia, Nitrate and Nitrite levels in the existing tank are zero.
 
Do you think my obsession with only using RO is wasteful and unnecessary?
 
Thanks, Steve

 

[Byron]

I'll start this off, as I came to it, though I comented in the other thread much the same as I will here I think.
 
RO should have zero GH and KH.  Your tap water at 8 dGH [I assume this number is in dGH, not ppm] is quite good for most fish, and all plants.  I would raise the GH for livebearers and other hard water fish though.  But aside from these, you should have no issues.  You could dilute the tap with RO for very sensitive soft water fish, but given the tank size you would be most likely to stay with somewhat more adaptable species anyway, so this should not be necessary.  Generally speaking, it is the very small species that can get issues with harder water.
 
Byron.

 

[goldfinger]

I have to agree with Byron I hate to waste water and decided not to use mine as it meant having to stick back the minerals into it when actually the tap water is okay!
Pros:
No need for Dechlorinator
You can control the quality level in your tank
Its great for topping up the tank
Cons:
Have to buy minerals to get goodness back into the water
Need buffer salts to get it where you want like discus fishes like soft so good with hardwater.
What a waste of good water even though its waste water from RO it can be used elsewhere.
Pre filters will need changing every six months (Costs)
Membranes once dried out will need changing practically cost of a new RO machine.
 
If you go down the route I suggest shutting valves to contain water in the system, so it does not dry out then flush it every other day which is a pain when you dont use all the water everyday.
These days some LFS will give you free RO water if you spend enough with them or they know you either way its cheap for 20 litres odd. Anything like 100litres plus it might be worth getting one if water changes are frequent enough. 
Get Ro with a flush system its worth it just to save the membrane.

 

[kirkster]

I'll start this off, as I came to it, though I comented in the other thread much the same as I will here I think.
 
RO should have zero GH and KH.  Your tap water at 8 dGH [I assume this number is in dGH, not ppm] is quite good for most fish, and all plants.  I would raise the GH for livebearers and other hard water fish though.  But aside from these, you should have no issues.  You could dilute the tap with RO for very sensitive soft water fish, but given the tank size you would be most likely to stay with somewhat more adaptable species anyway, so this should not be necessary.  Generally speaking, it is the very small species that can get issues with harder water.
 
Byron.

Thanks Byron/Goldfinger, So even though my water company states that my water is "slightly hard" and gives me a reading of 8.32 dGH, by tropical fish keeping standards you are saying that this number is actually quite soft and I should stay with soft water species?
Thanks for your input! This site is a treasure trove of information!

 

[TwoTankAmin]

Unless what comes out of one's tap is almost unsafe to use, there is little need in FW tanks for 100 RO. Nor will RO alone necessarily get you to a neutral pH and 0/0 GH/KH/TDS. Normally that required not only the RO but also a DI (deionization) resin as the final step. I use a portable 75 gpd ro/di unit and when all the carts are new, I get 0/0/0 and 7 or lower pH. But my tap starts at 7.1 and only 83 ppm TDS (about 4-5 GH and 3-4 KH). My mix is 50/50 ro/di and tap. I am now less interested in the pH than I am with the TDS.
 
As for how hard certain soft water species can handle more hardness than suggested on many sites depends on the specific fish. this might help you a bit:

General Hardness

0 - 4 dH, 0 - 70 ppm : very soft
4 - 8 dH, 70 - 140 ppm : soft
8 - 12 dH, 140 - 210 ppm : medium hard
12 - 18 dH, 210 - 320 ppm : fairly hard
18 - 30 dH, 320 - 530 ppm : hard
higher : liquid rock (Lake Malawi and Los Angeles, CA)

from http/fins.actwin.com/aquariafaq.html
 
As you can see you are about on the border of soft and medium hard. If you want to be a nudge about it, you should not need to mix in a lot of RO or RO/DI to lower your numbers enough to get down to 8. What you cannot do in your water is to keep fish that need really low TDS like wild altums or Licorice gourami. But most fish should be happy. Spawning some might be an issue, but you have not indicated this is important here.
 
But for anybody who needs ro or ro/di water, it is normally cheaper to make it yourself than to buy it.