Stupid Question.

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I read a post of Seangee's the other day about his RO unit and his soft water tank. I have read in the past that fish cannot live in distilled water for reasons I understand but cannot explain intelligently. I keep a male Betta in a tank and do his water changes with pure RO water. My reasoning is that they come from a high rainfall environment. I have noticed that he sits on the bottom a LOT and maybe looks a little scrawny. He eats good and his color is good. Am I doing a wrong thing with my RO water change regimen? The tank is crystal clear and the Java Fern is flourishing. I have no test kit and probably wouldn't use it if I did have one. After you've finished laughing I would like to hear some ideas.

 

[Colin_T]

Distilled water is pure water that has a pH of 7.0 and no mineral content.

Reverse Osmosis (R/O) water is meant to be pure water and have a pH of 7.0 and no mineral content, however there is a lot of variation between different brands of R/O units and how much stuff they remove from the water. It also depends on if the filter membranes/ media are in good condition or if they are old and blocked up. If the R/O unit is good, it will remove 99.9% of impurities and minerals from the water. If the unit needs new cartridges or is a cheap inefficient brand, it might remove 50-75% of the stuff in the water.

If the fish naturally occur in very soft water (water with low to no mineral content), they are usually fine in distilled or R/O water. However, if you put fish from hard water (water containing lots of minerals) into pure water (distilled or R/O), the fish will lose the minerals from its body (through osmosis) and usually die prematurely.

The main problem with soft water is the pH can drop rapidly and suddenly. It can literally go from 7.0 down to 6.0 (or less), overnight. This sudden pH change can kill fish.

Even water ways that are considered to have soft water will have some minerals in them. Small amounts of minerals get washed into rivers and creeks when it rains and the fish can utilise these.

Most fish do better with some minerals in the water, and having the GH around 50ppm is sufficient for most soft water fishes.

 

[seangee]

I started by mixing RO with tap water to get to 6dGH (100ppm). When I switched to straight RO I added minerals to bring this up to 2dGH because I also though they require some minerals. (I do however have some fish that are from very soft, acidic water). Losing the buffer was a concern but I do still have a detectable kH and my pH is hovering around 6. The RO unit has been filtering the water to a TDS of 10-20 ppm since new (tap is > 300).

Right now I am keeping a close eye on the MTS as their numbers have reduced and this may be due to a lack of calcium. I know Colin would be happy if they all just died, but I think they are an important part of my eco system, so may end up adding trace amounts of minerals.

FWIW I use Salty Shrimp GH+/KH+ in my other tank. Recommended dosage gives a dGh of 6 and dKH of 3 which IMO is much easier than Seachem, who would like you to buy multiple products to achieve the same thing.

 

[Byron]

I have basically zero GH/KH in my tap water and I have had this for all of my 30 years of keeping aquaria. I have gone through periods of buffering pH and raising GH. I no longer do, but I only keep fish from very soft and acidic waters, and most are wild caught.

The pH issue is worth exploring. Every aquarium will establish its biological system and this will include the water chemistry. The less we impact/influence this, the more stable will be the system. In my own case, with zero GH/KH, thee pH in all my tanks is on the acidic side, naturally, but it varies from tank to tank. I understand this is due to the unique biological make-up of each aquarium. For the past 10 years I have just let the tanks stabilize where they will; my only impact is a regular once weekly partial water change of somewhere between 60-70%. The pH in some tanks is in the low 6's, in others below 5 [I cannot measure below 5 and as this test shows very bright yellow I am assuming the pH is likely lower]. I tested the pH prior to the water change on these tanks for several months, every week, ands then sporadically every couple of months. Over a period of 6-7 years doing this, the pH in each individual tank never fluctuated from one test to the other of more than one decimal point; so one week it was say 6.2, and the next or some subsequent test it might be 6.3 but then 6.2 or 6.1...you cannot have more stable water. And that is what you want in any aquarium, stability.

I should also mention that my tap water pH is 7.0, but it is how this is achieved that is important. The natural pH of the reservoir water is at or below 5, and in 2001 Vancouver began adding soda ash to increase the pH to 7 in order to combat corrosion in the pipes. This has caused no problems, other than the first week they did it and I was not aware of it, and two days after the water changes I noticed that every single crypt in my tanks had melted into a pile of mush; crypts do not like sudden changes in water chemistry. But otherwise, no issues. This is temporary, and during the water changes the pH may rise a couple decimal points, but within a few hours it is back to where it was because the tank's stable biological system keeps it there.

BTW, no question is stupid when it is asked to learn.

 

[Back in the fold]

Thank you Byron.

 

[PheonixKingZ]

Not a stupid question at all!!

It seems that all of the above, is waaaayyyyyover my head....(If I still have one, let me check real quick......)

 

[Back in the fold]

Not a stupid question at all!!

It seems that all of the above, is waaaayyyyyover my head....(If I still have one, let me check real quick......)

No. This is not way over your head. If you don't immediately grasp it then re-read it a few times. This is something that is vital knowledge for any aquarist. Water chemistry is crucial and so is your understanding of it. The more you know all the whys and wherefores of water the more successful you will be.

 

[PheonixKingZ]

I understand the basics, but I don’t know the real specifics.