Topping off with RO/DI Water

  • Get the NEW AquariaCentral iOS app --> http://itunes.apple.com/app/id1227181058 // Android version will be out soon!

ZorroNet

AC Members
Sep 21, 2013
510
0
0
45
Paxton, FL
flfarmersmarket.com
Real Name
Dave
Okay... first let me put a disclaimer:
I have never used RO/DI water; I do not have an RO/DI unit. I do know that this strips the water of pretty much everything including minerals. This is a question of theory, and it will likely cause a debate. I'm okay with that :)

Here's what I'm thinking about and putting out to the masses for discussion...
I was thinking about creating an automatic top off system for my tanks. I don't have a well, so this is plain old Paxton tap water I am working with. So, rather than using a bucket and siphon, I was thinking about buying an RO/DI unit to install inline to feed an auto top off system. The plumbing part should be simple enough... float + valve + water with enough pressure = auto top off. There's no reason to debate the plumbing design... I don't think so anyway.

The question is: How would this affect the aquarium's water long-term? Would I need to supplement minerals being stripped from the top off water? I ask because when I think about the aquarium as a relatively closed system, it seems like many of the minerals would just remain in the water unless they are removed through water changes or consumed by plants. Kh, for instance, should not change much, but over time I would expect for it to drop gradually if I don't supplement minerals to keep it up. Addition of fish food does increase the mineral content of the aquarium's water, even in the form of fish and snail waste, minerals are being added to the water daily. That's one reason for water changes right?

BUT I also have another plan I need to fill you in on that has a bearing on what will be going on chemically speaking. I intend to add some terrestrials to the top of the tank to soak up some of those lovely nitrates that aquatic plants don't consume so well. Now... water changes are something I might be able to throw out the window more or less. I'm not trying to be lazy, just more automated.

Okay... I'm ready to release the hounds. Let's try to keep the conversation more scientific and less opinionated if we can :)
[Trumpet Sounds] GO!
 

Byron Amazonas

AC Members
Jul 22, 2013
986
2
18
73
Pitt Meadows (within Greater Vancouver, BC) Canada
Real Name
Byron
Since you mention reducing/eliminating water changes, I will assume the "topping off" is just replacing evaporated water. As water evaporates, it leaves behind the mineral salts. So this topping off is not likely to make much difference, but very slowly the water will become softer. The initial GH and KH plus the fish load, plants, feeding, etc all factor into this. Fish and plants take up minerals from the water. In the case of plants, I would expect the micro-nutrients to be depleted long before the macros like calcium, but again this depends upon the initial water composition. As for fish, it depends upon the species as to how they fare.

Water changes do much more than what is being discussed here, and their effect on the system is thus much greater. There is no way around them for the benefits to fish and plants.
 

ZorroNet

AC Members
Sep 21, 2013
510
0
0
45
Paxton, FL
flfarmersmarket.com
Real Name
Dave
Yes, "topping off" refers to maintaining the water level lost to evaporation by adding water back to the tank.

That is the kind of information I am looking for, Byron. I'm not as well-versed in specific nutrients and minerals as I am in other things, and I've made it this far without adding fertilizers or minerals in addition to doing regular water changes. I know the water changes are a source of minerals added to the tank (when using tap water), and that's why I asked the question in regard to changing to RO/DI water. I'm thinking outside the box here, but I don't want my fish and plants to suffer if I am missing something. Thank you for your input!
 

Rbishop

Administrator
Staff member
Dec 30, 2005
40,727
452
143
70
Real Name
Mr. Normal
As long as top off is for evaporation and not to replace water changes it will be perfectly fine.
 

ZorroNet

AC Members
Sep 21, 2013
510
0
0
45
Paxton, FL
flfarmersmarket.com
Real Name
Dave
*FACE PALM*

Thinking outside the box wasn't as smart as I thought... Couldn't I just get a carbon block inline filter to remove chlorine for much less? Then I won't have to worry about minerals. I could then create a float controlled top off like I was talking about and add an overflow system. Then I could forget about water changes because the water would be in a constant state of being refreshed. Duh! Why didn't I think of that first?
 

Rbishop

Administrator
Staff member
Dec 30, 2005
40,727
452
143
70
Real Name
Mr. Normal
Search Li's threads on here...he did an auto fill system with in-line dechlorinator using Prime added.....
 

ZorroNet

AC Members
Sep 21, 2013
510
0
0
45
Paxton, FL
flfarmersmarket.com
Real Name
Dave
Thanks, Bob! That looks way bigger than what I would need, but I'm sure I could scale it down and accomplish the same results on a smaller scale. No need to re-invent the wheel when someone is already rolling :)
 

Pinkey

AC Members
Nov 16, 2004
221
20
18
Denver
Real Name
Nate
Couldn't I just get a carbon block inline filter to remove chlorine for much less?
I have a 130 with an open top (plenty of natural evaporation). The water flows through 12' of planted trough (I'm pretty sure you have commented on pics of it in the past, if not I'll post a pic here). I have to add 3-4 gallons of water twice per week to compensate for evaporation. Our municipal water is treated with chloramine which, from what the LFS says takes a lot longer to clear out of the water. I add water directly from the tap and have tested from chlorine just after adding a bucket and it still comes up as no chlorine present.

My system is about 150g, if I add 4 gallons that is the equivalent of about a 2.5% water change. The chlorine is diluted approximately 40 times resulting in no reading. I have very hard water with so much buffer that the pH in the tank has never read anything other than 6.8.

Before you worry about spending any time or effort on this system (I, too, am infatuated with automation) do an experiment.

1. How much water do you add now to compensate for evap?
2. How many gallons is your setup (Include sump)?

Once you have that ratio you can take (pick English or Metric) 1 liter replace however many ml of water according to your ratio, and then test.
 

wesleydnunder

Discus Addict
Dec 11, 2005
2,752
167
66
Gulf Coast Texas
Real Name
Mark
I have a 130 with an open top (plenty of natural evaporation). The water flows through 12' of planted trough (I'm pretty sure you have commented on pics of it in the past, if not I'll post a pic here). I have to add 3-4 gallons of water twice per week to compensate for evaporation. Our municipal water is treated with chloramine which, from what the LFS says takes a lot longer to clear out of the water. I add water directly from the tap and have tested from chlorine just after adding a bucket and it still comes up as no chlorine present.

My system is about 150g, if I add 4 gallons that is the equivalent of about a 2.5% water change. The chlorine is diluted approximately 40 times resulting in no reading. I have very hard water with so much buffer that the pH in the tank has never read anything other than 6.8.

Before you worry about spending any time or effort on this system (I, too, am infatuated with automation) do an experiment.

1. How much water do you add now to compensate for evap?
2. How many gallons is your setup (Include sump)?

Once you have that ratio you can take (pick English or Metric) 1 liter replace however many ml of water according to your ratio, and then test.
This subject was addressed by RTR years ago. Along with the minute volume added to the tank which dilutes the chlorine concentration , the chlorine quickly gets "used up" in oxidizing organics with which it comes into contact soon after being introduced into the tank. In this instance, the impact of chloramines on the tank is probably so negligible as to be nonexistant.

Mark
 
zoomed.com
hikariusa.com
aqaimports.com
Store