Ro / Di Unit Water For My Aquarium?

[bradmarsh]

Strange question probably but i think i could do with some advice. I have a reverse osmosis and deionisation unit for my window cleaning business (waterfed pole system) but i actually bought it from an aquarium shop. I was thinking of using pure water during my 20% water change weekly. Seems like a good idea as the lack of content (TDS) will help to dilute ammonia etc down with clean water. pH is unaffected by the RO\DI unit.

The only problem is that i read somewhere that guppies prefer hard water??? is this true? should i just use tap water? does anyone else use an RO/DI unit?

Due a water change soon... what should i do?


thanks

brad

 

[STRiDER]

Hi there

Firstly we need more information really.
What is the PH in your tank and what is the PH in your tap water.

It is true that a RO unit will not change PH right away, however it will seriously affect your Carbonate Hardness (KH). RO Water has almost no Carbonate Hardness and the total Hardness in your tank will therefore drop.

Carbonate Hardness is linked to PH buffering. What this means is that if your hardness is too low it can lead to a PH crash (PH dropping to below 5) and thats quite bad.

Guppies will tolerate a fairly wide range of PH (6.0 to 8.2), so if your tank currently has a PH in this range I will sugest leaving everything as is.

Hope this helps

 

[bradmarsh]

sorry, my experience with the RO/DI unit are really in pH, TDS, (i use it for window cleaning). i have some basic water chemistry from swimming pool plant rooms too. fish tank water is new to me!

i assumed that pH in water would remain consistent once the tank is cycled. the pH of the tank water, RO/DI water and tap water are all at 7.2.

i also assumed adding the ro/di wouldn't affect it is they are similar, you mentioned the carbonate hardness of the tank water would be reduced after numerous changes correct? what part does this play? what would the effect be on the tank / fish?

 

[xoedusk]

Tap water usually dillutes ammonia and other nasties just fine. Depends on the readings, of course. As Strider suggested, posting your tap and tank stats would help us give some advice.

Does RO/DI water not leave streaks on windows?

 

[crazie.eddie]

In addition to the above questions, what fish are you keeping?

Unless you're breeding fish, most fish can acclimate to different water parameters.

 

[bradmarsh]

guppie (6 females). dont have results to hand at present, not at home, sorry. just assumed as aquarium stores sold the RO/DI unit that it would be beneficial??? i thought generally it would be better?? thinking probably isn't my strongest point!!!

so what conditions is an RO/DI unit required? useful? beneficial?

Do you think tap water would be better than purified water?

sorry for my lack of knowledge. at least i asked before making a mistake!

cheers all

p.s ro/di water dries streak free with no residue / water marks!!! try it!

 

[Liam]

Most people who have hard water with a high PH use RO water to soften the water and get a lower ph for soft water fish, eg discus eggs wont hatch if the water is too hard. Some fish come from water that is almost pure water others come from harder or very hard water with lots of dissolved solids, like calcium and magnesium. Even very softwater fish cant live in purely RO/DI water in an aquarium, ph crash is one problem. Guppies prefer harder water so any medium hard water is good for them. People keeping marine aquariums use RO to purify the water they then add salt and the essential minerals. If you keep soft water fish and have hard water then mixing RO water in consistant amounts is good for the fish.

 

[bradmarsh]

thanks liam, thats a really helpful post. so my guppies will actually prefer tap water?

As we are in a hard water area (300 ppm TDS tap water). Do you think that it might be too hard or will that be ok?

is it worth testing the fresh water i add post aqua-safing to give a more accurate TDS? if its too high i could add a small amount of RO/DI water to the tap water to reduce it? what do you think?

thanks

 

[STRiDER]

Hi Brad

Before I ramble on about chemistry let me say this:
I would not use RO water in your setup. Your PH is perfect for your guppies and they will tolerate hard water.
Using tap water also makes your life easier

------------

You say that the TDS of your tapwater is 300ppm.
This does not help much though. TDS measures ALL dissolved salts in your water. This does not mean much to an aquarist though. We need to analyse what the TDS is made up of. (all the different salts and minerals)

(NOTE : You can have a high TDS with very low hardness and vice versa. TDS does not equal Hardness)

For example: we measure the NO2, NO3 and other levels seperately because everyone means something different.

When you are talking about hardness, you need two measurements: GH and KH

Here's the explanation

------------

With water you have two parameters indicating the hardness.
1. GH : General Hardness (Also called Total Hardness)
2. KH : Carbonate Hardness (Also called Alkalinity)

GH consistes primarily of dissolved calcium (Ca) and magnesium (Mg)

KH is principally composed of bicarbonate ions (HCO3-) and carbonate ions (CO3-). KH is known as your water's buffering capacity.
This means your waters ability to neutralise any acid.

----------

Now here is how this all work...

Your fish continuously produce ammonia (from excrement and through their gills) as they feed. This ammonia is converted to nitrates by the bacteria in your filter. When this conversion (from ammonia to nitrate) occurs, H+ protons are released into the water. These H+ protons acts like an acid, ie it wants to lower the PH of the water.

However, the H+ protons will bind with CO3- ions.
This means that as long as you have Carbonate hardness (KH) these H+ protons cannot lower PH.

However, when all the KH are used up, the PH will suddenly drop. This is known as PH crash and quite a few aquarists struggle with this phenomenon. It is common in soft water areas and you have to constantly raise KH to prevent it.

This is also why you do weekly water changes - to remove excess nitrates.

...gasp...

----------

A TDS of 300 is not off the scale. Most water companies specify a upper limit of 1000 and water becomes undrinkable only above 2000ppm.

If you want to add RO water it is important to know what the KH of the water is. (Can be measured with a test kit).

Desirable KH levels depend on your type of fish really, but I will suggest to keep the level above 80mg/L to ensure a buffer that is high enough to prevent PH crash.

By adding RO water you might accidently lower your KH below this level. (That is also the reason why you should NEVER add 100% RO water to ANY freshwater tank!! - It is always done in a controlled percentage way to ensure correct KH levels.)

GH is dependant on fish species.
GH is rated as follows:
0 - 60 mg/L : soft
61 - 100 : slightly hard
101 - 200 : hard
>200 very hard
(Remember GH does not equal TDS)
Guppies will thrive in a wide GH (appr 60 to 200).

----------------

So where does RO units for aquarium use come for? What are they for?

Firstly they are a must for all Salt water aquariums. KH is not a problem here as large amounts of salt is added after Ro filtration raising the KH to between 105 and 125 mg/L.

Secondly, people struggling with a high PH combined with high Hardness will benefit from an RO unit. It is almost impossible to lower PH if the KH is high (Large buffering capacity). By lowering the KH, it becomes possible to lower the PH, either manually or automatically by the H+ protons in the tank.
In this instance the RO water is only added in certain percentage as determined by KH levels and NEVER 100%.

-----------------

Lastly, I hope I did not go into too much detail, and also I am not a professor of biochemistry, this information was learnt by many months of research. If I made mistakes, please feel free to correct me.

---------------

In conclusion Brad, I would not use the RO-water. It would help if we know the GH and KH levels, but I suspect your tank is doing fine as it is - and the golden rule in fishkeeping:

If it works - leave it!!


Happy fishkeeping
Andre dT

 

[raptorrex]

sorry, my experience with the RO/DI unit are really in pH, TDS, (i use it for window cleaning). i have some basic water chemistry from swimming pool plant rooms too. fish tank water is new to me!

i assumed that pH in water would remain consistent once the tank is cycled. the pH of the tank water, RO/DI water and tap water are all at 7.2.

i also assumed adding the ro/di wouldn't affect it is they are similar, you mentioned the carbonate hardness of the tank water would be reduced after numerous changes correct? what part does this play? what would the effect be on the tank / fish?

the natural buffers that maintain steady ph are removed in RO water, leading to massive swings, as the water has no ability to control them. for saltwater this is not so much a problem, as the water is a cocktail anyway, but in fresh . and also it is very wasteful of water a ratio of 4 or 5 just to get one RO unit, is to be honest obscene, IMO, at a time when we all seem to be running out of water.

 

[bradmarsh]

thanks for your help all. think ill stick to good old tap water!

keep the RO/DI for windows!

I agree its wasteful boboboy! thats why i collect the waste from my unit and use a shureflow pump to re-cycle it into the unit when i fill the waste water butt. i can do this a few times and then the membrane clogs. just means i flush the system once a day for two minutes. keeps waste to a minimum. the remainder i use to water indoor house plants etc.

dont think i know anyone else who does this but i do try and do my bit... thanks for the concern