Ion Exchange Resins

[stormhawk]

Hi all, while going through a Japanese killie hobbyist's site, I came across this idea of his showing a DIY ion exchange reactor. The page was translated using Altavista's translating service. Reference is here:

Test Tube Reactor

It looks quite easy to make and an easy alternative would be the CO2 bubble counters that we usually use in CO2 injection for planted tanks. My question is, what exactly is the use of ion exchange resins in the tank?

[shortman]

My question is, what exactly is the use of ion exchange resins in the tank?

It is use to reduce the hardness of the water. Azoo have some WATER SOFTENER resin that is recyclable. The resin will change color after it have absorb the ions/cation and fully charged. Then recycle the resin in warm salt water to dis-charge it.

http://www.azoo.com.tw/azoo_en/modul...eview&bkid=188

Best Regards

[stormhawk]

Kho, thanks for the tip, but another question. If this resin changes colour from brown, to what colour does it change to when it is fully "charged"? I may intend to use this in some tanks.

Also, to add on, I did some additional research on the web and it was mentioned that for the resin to have the best effect, it required a slow flowrate of water. Is this true?

[whuntley]

Ion exchange is a vague term.

Simple zeolite or even peat can exchange ions and replace Ca, Mg and Fe with Na to "soften" water. Most complete ion-exchange systems have both anion and cation exchange resins, so they can replace both kinds of ions, replacing them with hydrogen (H+) and hydroxyl (OH-) ions that combine to form pure water (H2O). They are recharged with strong acids and strong bases. Not a job for the amateur chemist to do at home.

Deionizers can even make water that is purer than distilled, for the volatile gasses that can get into distilled water are often also eliminated.

There is no place for either deionizers or water softeners in fresh-water aquaria. They may make some sense in some reef situations, where the aquarist wants to start with a perfect blank slate when creating the salt water with blended minerals like Instant Ocean or Coralife.

RO water is as pure as is ever called for, even with rainforest fishes. It is cheaper and easier to work with without accidentally killing your fish and plants.

If the salinity is increased in a water softener, the water is often poisonous to fish and plants unless special precautions are taken to assure ample potassium is added back. Some softeners are recharged with potassium salts and cause blood electrolytes to go out of whack the other way. Blood electrolytes are even more messed up with deionized and distilled water often times. Please don't do it.

Slow flow is required for the same reasons as filtering out chloramine with carbon. Time of contact is critical and not testing is often a quick road to catastrophe. Proper testing requires a broad range of tests, too. Na, K, GH KH, pH, tds Cl and NH4 are a good starting set. Personally, I can't be bothered, so I save DI water to use in my car battery, but never in a tank.

Deionizing and chloramine filtering need to be done in a pressurized container, for effective filtration to happen. The bags you add to your tank or filter basket are, IMHO, a waste of time. They just add uncertainty to your water and are almost as likely to release nasty stuff as trap it.

The LFS owners could wring my neck for saying all this, because they get a huge markup on all this stuff.

Wright

[whuntley]

PS. You need an iron test kit, too, so you can add back chelated iron to replace that that the DI unit is certain to remove.

WH

[stormhawk]

Wright, thanks for the informative insight. But in this case, I was wondering about the use of these made-for-aquarium "ion exchange resins". If all they do is to soften water then I guess using just peat pellets in a slow filter might do the same trick.

[Slaigar]

Very informative post, Wright.

Prices for resins may not be practical for the hobbyist. The water softening bags that hobbyists have access to at LFS' are exchanging Na with the Ca and Mg in the water. Then recharging it is just placing the bag in into an aquarium salt solution. For freshwater tanks, it is just unnecessary since, as Wright said before, RO water is cheaper.
It may be best just to stay away from both.

I would stick with peat to soften water. It is slower and tinges the water tea colour, but it leaves no excess Na+ in the water. Not the best for a planted tank set up.

[whuntley]

Wright, thanks for the informative insight. But in this case, I was wondering about the use of these made-for-aquarium "ion exchange resins". If all they do is to soften water then I guess using just peat pellets in a slow filter might do the same trick.

No. Peat pellets, if unboiled and not completely rinsed can raise hell with your water. They will add a whole lot of humins and organic acids and often are the cause of huge increases in salinity (sodium, anyway). Some (all here in the US) have lots of lime that isn't on the label. Without it they have enough acids to badly burn seedlings. Boiling and rinsing removes that, too, of course. By that point they are pretty worthless as water softeners for the Ca in the lime kicked out that huge burst of Na and used up all the ion-exchange sites.

For simple softening, zeolite chips are far better and will do less damage. At least one aquarium brand, marked up about 2000% above normal, would be Ammo-Chips. Ammo-Carb is a mixture of two mischief-makers, zeolite and activated charcoal chips.

You need to know if the "ion-exchange resins" are for cations only (simple water softener) or both. The effects are different. The former will add so much sodium to your water that it may become toxic as potassium is overbalanced. The latter will mess with *all* the critical blood electrolytes and remove many essential trace elements in the process.

If you want to lower hardness or reduce buffering (alkalinity) to lower pH with peat or leaves, then dilute your water with cheap RO water to get the correct KH and GH, but always before it goes into the tank.

The problem with in-tank treatment is that the exchange material can saturate and a new substance coming into the tank can cause it to suddenly dump a huge dose of ammonium or copper or lead or ??? that it had stored. The new intruder always gets blamed, so the store keeps selling these nasty products. As you can tell, I really do not like them, tho I have tried most over the years. ["Gullible" is still almost missing from my dictionary, I guess. :wink:]

Wright