# Resins and their use in the hobby



## Antoni (19 Jan 2012)

Hi guys, 

few days ago, I came across some readings about the resins and their use in water purification systems and aquatics respectively.

So I start wondering, is it the right choice in matter of effectiveness and cost to use resins to soften and purify water? This could be useful for shrimp keeping and planted tanks too. 

Many of us use RO water nowadays, but the cost of the decent system and the volume of water we waste to produce 1 unit of RO water makes me think - is this the best and the most wise option?   

After doing much of a reading I have found out that there are 2 main types of resins having application in the aquariums: 

*Anion exchange resins and Cation Exchange resins
*
The Anion resins exchange the negatively charged ions from the water, such as : Chlorides [Cl-], Sulfates [SO4=], Nitrates [NO3=], Carbonates [CO3=], Silicates [SiO2-]

The Cation resins are responsible for the absorbtion of positively charged cations as Ca and Mg, which is the reason for the lowering of the Kh.

Based on the above, to get a pure soft water, suitable for use in the shrimp/planted/marine tank, we will need to combine the 2 types of resins. After some research I found that actually the so called mixed bed systems are widely used in the window cleaning systems. 

The price for a liter of those resins is about 5-10 Pounds depending on the brand. They are not rechargeable, but should last quite long. 

*Some thoughts: 
*
Now, I'm not quite sure, is it possible to use these resins, straight in the aquarium, as there are 2 types of resins: macroporous and microporous resins. The latest are used in the water purification systems for drinking water but they are not suitable for aquarium use, as they will get clogged very fast. But we could use them to treat the tab water, prior aquarium use.

I'm not sure, what is happening with the Gh if only the Cation resins are used - they are not affecting the CO3? Do we really need to get the Gh down too for general aquarium use? How the flora and fauna would react on Kh 0, Gh 16 for example? Darren or Clive, please help me out on this!

There are also rechargeable resins, but for the anion resins we will need some strong acids NaOH, which makes it not very convenient and dangerous.

The cation resins can be recharged with table salt, but IMO this is not the best solution, as the collected Ca and Mg cations will be exchanged with Na, which afterwords will be released in the aquarium water. as we all know, the Sodium is not good for the aquatic life. I found that possible solution could be recharging with KCl, where the K cation will be exchanged for the Mg and Ca. This could be even beneficial for the plants  :?:


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## ceg4048 (19 Jan 2012)

Hi Antoni,
               While the benefits could be something invert keepers might be interested in, I can't see any benefit for plants generally as this would be the same issue faced by RO users. There is no point removing compounds the plants needs just so that you have to add it back. Why would you want to remove NO3, Fe, Ca and Mg? There are plenty of examples of inverts being kept in high TDS water and those inverts which require low conductivity would be best served by using RO which also removes toxins.



			
				Antoni said:
			
		

> I'm not sure, what is happening with the Gh if only the Cation resins are used - they are not affecting the CO3? Do we really need to get the Gh down too for general aquarium use? How the flora and fauna would react on Kh 0, Gh 16 for example?


 A zero KH is not necessarily desirable since carbonates/bicarbonates have osmoregulatory significance.



			
				Antoni said:
			
		

> The Cation resins are responsible for the absorbtion of positively charged cations as Ca and Mg, which is the reason for the lowering of the Kh.


No, CA and Mg are related to GH. In any case this is having the cart before the horse. Plants don't care about GH just for the sake of GH. They care about having access to Ca and Mg, so removing Ca and Mg is pointless.

The only reason for employing these resins or even RO for that matter is for fish and inverts not for plants.

Cheers,


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## Antoni (19 Jan 2012)

HI Clive,

thanks for the answers!

I do not argue, that for the planted tanks, RO or very soft, pure water is not necessary, but it is fact that many people use it. That is why I raised the question. 

For the shrimp keeping especially CRS, CBS and their variation, pure soft water is a must. I personally use RO water to spray my wabi kusas, as tab water, creates limescale deposits on the glass.

RO give good purity but DI resins polish the water even further. That is why they are used as a final stage after RO. However my point is, that the RO is not very sustainable method. To produce 50 gallons of RO water you send to the drains about 200 gallons, which is huge waste. I believe we need to be aware of that! 



> A zero KH is not necessarily desirable since carbonates/bicarbonates have osmoregulatory significance.



But we could mix it with tab water to get the desired level of Kh. /No matter for fish keeping, invert keeping or planted tank geeks, who love to have the ''right'' parameters/

Maybe I didn't build up my question the right way, but the idea is not to argue is it necessary to use RO/DI water, but to compare the effectiveness and convenience of resins against RO for those who use it.

I believe that the resins can produce purer water in more sustainable and hassle free way. I just cant figure out exactly what resin is the best, can we use the Cation resins only to soften the water, can we use resins straight on aquarium water, as the marine systems and recently ADA do.


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## ceg4048 (20 Jan 2012)

Hi Antoni,
              Resins are normally very specific in the ions they filter out, so using just resins alone does not guarantee the elimination of toxins that are in a water solution that can damage your invert. The only reason for having other filter elements in an RO unit is to protect the RO filter medium from damage, so for example, a multi-stage RO unit may have a Carbon cartridge  but that it to remove chlorine which attacks some types of RO membranes. There is absolutely no way that any resin removes more things from the water than an RO membrane - absolutely no way. The reason is simple; water molecules are very small. In any water solution the water molecule H20 is virtually always the smallest molecule in that solution. The membrane has such tiny "perforations" so that only the very smallest molecules can find it's way through the membrane. All these other ions you mention and that we are concerned with are larger than a water molecule so they do not pass through the membrane. Effectively therefore an RO membrane is just a net which captures everything except for H20.

Therefore, passing water through an RO eliminates not only Ca, Mg, NO3, K and so forth, but also viruses, bacteria, pesticides, herbicides and anything else harmful to your invert. The resins cannot do this and will not reduce the TDS as much because they will not attract some of the compounds in the water that contribute to TDS.

So comparing RO to resins such as HMA is comparing apples to oranges because they do not do the same things. So if your goal is to reduce GH to zero but to allow the other parameters to fall where they may, and if there is such a resin that adsorbs nearly 100% of Ca/Mg, then yes, this would be a less wasteful alternative. Some people use HMA in lieu of RO because they worry about heavy metals in the water supply but perhaps they are less concerned with other nasties and they do not incur the penalty of wasted water. However, if your goal is zero conductivity, or removal of bacteria/viruses then you'll have to take the penalty, because no combination of resins will achieve this as effectively as RO. A multi-stage filter containing the resins that adsorb your chosen parameters would be the best path however if you wanted to avoid the waste water penalty - assuming the resins work as advertised and have decent longevity. This means a lifetime of testing though...  

Cheers,


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