[davido]

I'm about to purchase a RO filter this weekend, but have a few doubts because RO is totally new to me.

First some background. Mine's a 40 gallon community tank. Medium planted, Aquasoil substrate, with lots of Tetras and shrimps. About 30% WC weekly.

Been using filtered tap water all this time. My tap water is a bit unpredictable. It depends on the season, level of the dams and what the water department is doing. PH can be below 7 to 7.5. TDS 60. Not very sure but I know they fluctuate.

The reason for the RO unit is because I noticed my PH, GH, KH, TDS, nitrate are slowly going up and I want to keep them low.

Since setup, PH went from 6.8 to 7.2, KH from 1 to 3, GH from 4 to 6, TDS from 80 to 160, nitrate from 10 to 40.

I'm struggling to keep my PH and nitrates low and the impurity in my tap water is not helping. I'm also seeing small BBA growth and I suspect its because my tap water contains high phosphate because its the dry and hot season now.

So I was thinking to use RO water. As I'm new with RO, am I right to assume that it will help lower my PH, nitrate and phosphate?

During WC, I will run a hose from the RO unit directly into my tank. How long will it take to fill up about 30 liters of RO water?

Is this the correct way to use RO water? It goes directly into the tank. Or do I need to add minerals, or keep it overnight, etc?

 

[Hardstuff]

You really need to add the water from the R/O to a holding bucket or buckets or ideally 1 container even a small 10 or 20 gallon tank. The issues you will be having will be overfilling the storage container. Some r/o's can be purchased with a storage tank. I would strongly urge you not to take water from the r/o storage tank since the TDS will vary all the time and bacteria will build up in the storage tank itself.

I have been using r/o water for 6 years now. And I strongly feel you need to add a Gh booster and a Kh buffer as well as additional trace. What I do is add calcium sulfate, magnesium sulfate, and potassium sulfate. Usually about 3 parts Ca to 2parts Mg to 3parts K ratio. You will need trace for fish but others may say you do not need it but I know I have seen healthy benefits from adding additional fish trace. Seachem sells it and its not expensive. The only other thing you will need is baking soda to bring up what ever kh you desire.
Mix all in your container and add enough Gh booster and trace combined to get desired Gh than add in the buffer. Generally the ph will not be an issue. You can pick a time closest to tank ph and container ph and go for it providing you do not exceed 50% and add it slowly. In the event that the ph are way off you can add a little vinegar , just a few drops per 10 gallons to get the ph closer.
So yes, you have to add minerals back into the r/o and never add directly to the aquarium!
It sounds like your tap water is soft so your membrane in the r/o should last a long time provided you follow pre carbon filter instructions for longevity. You might only need 1 carbon block in front of the membrane. You will have consistent water but make sure to adjust the flow restrictor for maximum efficiency to minimize waste water. Usually 2 to 1 or 3 to 1. The first number is your waste water the second number is your process water.
Nitrates should be zero, PO4 should be zero but you may pick up some PO4 if you do not rinse the pre carbon filters enough but the PO4 will settle down to zero after a couple weeks. TDS in your case will stay steady between 15-30ppms steady for years if used for your 40 gallon breeder especially if you change water every 3 to 4 weeks verse every week. But after you mix in the GH booster and Kh and trace your TDS should fall between 120-190ppms which good for soft water depending on how soft you want it. Hope this helps

 

[jr125]

Good advice.

 

[Linwood]

I think you may be off on a tangent, frankly. Does your water have measurable nitrates? The increasing nitrates may be an indication you have inadequate plants and/or inadequate water change, unless you actually have nitrates in your tap water.

And are you buying an RO system, or RODI system? With an RO system, you will still have some TDS in the water out of the filter; with RODI you should have near zero, it is very close to distilled water, and as mentioned above needs to be remineralized. Even RO water likely needs to be remineralized, as Hardstuff mentioned above.

Most municipal water is higher than 7.0 PH, as an anti-corrosive measure. So I'm surprised your PH was ever 6.8 using tab water. It's not impossible, just seems unlikely. Nothing you mentioned above really needs PH under 7. I mention this because it is much more difficult to achieve a stable environment at 6.8 than it is at (say) 7.8. Low PH means little buffer (generally speaking in aquariums) and little buffer means small changes can cause largish swings in PH. So take some care in mixing your water if you plan to aim to get back to 6.8. Be sure to completely, thoroughly aerate it before measuring PH. And if you are aiming in the 7.0 range, be sure to add very, very little KH (e.g. bicarbonate of soda for example), like just a pinch. As an example, a dKH of 1 requires only about 0.7 teaspoons per 40 gallons of RODI water, less with RO water as it will have some in it already, and you may need even less than dKH=1 to get under 7.0.

If you still want to go that way, my own suggestion is Seachem Equilibrium (2 teaspoons per 10 gallons) and Sodium Bicarbonate (very little like 2/3rds of 1/4 teaspoon per 10 gallons), should give you somewhere around dKH=1 and dGH=4 EXCEPT for what is already in the water if RO not DI, so measure the first batch and cut back proportionally.

 

[davido]

Thank you all. Your replies are certainly very educating. Yes, my tap water contains nitrates. And I know I'm overstocking my tank, and its not heavily planted enough to absorb all the nitrates. These factors combined are probably causing the nitrates to rise. And I wanted to counter that by using RO water which would contain zero nitrates.

However after reading your replies, I can see that I need to remineralize the water. And the flow is really very slow. I'm going to defer my RO purchase until I do more research about RO. Because I'm not a fan of remineralizing because its not practical for me. To do that, I need to mix the minerals into three large buckets, then siphon the water into my tank. Problem is my tank is already at shoulder height, and using siphon is quite a lot of work (to raise the bucket higher than the tank - oh boy)...

I didn't know there's a difference with RODI. I thought it came as a set of particle filter, carbon filter, and then RO membrane. I'll ask the LFS for more info too and educate myself, but as of now, I'm not too encouraged with using RO.

 

[Linwood]

Here's a brief primer to help in your research.

The particulate filter takes out (usually) neutrally charged large particles like mud, rust, etc.

The carbon filter(s) will take out some chemicals, but in particular removes Chlorine from water treatment, which is harmful to the RO filter.

The RO filter will take out some percentage of most contaminants in the water, the percentage varying by temperature, pressure, and specific membrane. But for the sake of argument let's say 95% is removed.

Then, if you have one, the DI filter takes out negatively and positively charged ions in the water, hence "De-ionization". Most items going into solution do so by separating out into a negative and positive ion, and this electrical action to remove them takes out a large portion of the rest.

So say you start off with 100 TDS water after it gets through the carbon filters (and let's assume that is all in solution, i.e. "dissolve" solids). The RO filter then outputs water with 5 TDS, and then DI filter takes it to zero (OK, not precisely zero, but most aquarium quality meters will read zero after a DI filter).

If you start with 300 TDS water, RO might be 15, and RODI should still be zero. If it's 600, then RO may be 30, RODI is still zero.

This is why you will see some people use RO water without remineralization, depending on what they start with, and the quality of their filter -- it may actually be "mineralized" enough for them, if they are trying for water that is very, very soft. But it depends on the input water. If you start (as it sounds like you will be) with very low TDS to begin with, a RO filter (without DI) is still going to be darn close to zero.

Water that is too soft, i.e. near zero TDS, is not healthy for fish. It throws off the osmotic balance, in a loose sense sucking healthy stuff out of fish membranes (such flows usually go from high to low concentrations, which is why a RO filter is "reversed"). I have never seen any scientific study to say just how low is safe, but everyone seems to agree that zero is bad. If I were using RO water, with my 250 TDS input, I might not worry. If you are doing so with 60, my GUESS is you would be in the danger range without remineralization.

Now another common way RO or RODI water is used is dilution (someone around here had a signature saying "the solution to pollution is dilution" and that is very true). You can use 50/50 RO water with your tape water, to drop the TDS from 60 to 30 +/-. That works well when you are trying to reduce hardness, but it is marginally effective if your water is high in nitrates. By the way, how high? Is that really the issue?

A natural issue is "why RODI instead of RO" if it takes out 95% of the bad stuff. Well, many of us are a bit compulsive, and once you get all the way to RO you might as well get rid of it all and build your own water just how you want it. But that's not a necessity, but a choice.

Anyway...

Should you decide to do RO or RODI and remineralize, there are other solutions than siphoning. I got a big trashcan (Rubbermaid grey cans is frequently used and accepted as not introducing harmful chemicals). I then bought a pond pump. I toss it into the can to mix (it just swirls the water around). When the can is on a dolly. When I'm ready to put it in the tank, I roll it over, put a hose on the pond pump, and it let pump the water up into the tank. If you do this, you need to get a pond pump that has enough "head pressure" to raise the water to whatever height you need, plus a bit more to have good flow. Many will only go 3-5', some 7-9'. Another alternative if you are handy is a bilge pump - they pump much higher, but cost more, and need 12v power -- I use that as I am moving a lot of water and just plug it into a transformer I got with LED lights. What I did was put a piece of PVC on the end, cap it off, and drill a bunch of holes in it so I get more of a spray when the water comes out than a stream, to keep from disturbing the tank so much.

But... back to the "solution to pollution is dilution"....

If you are over stocked, and building up nitrates, even if your input water has some (let's say 5ppm), the simpler answer is probably to change water more aggressively. If you are changing at 40ppm or even 20ppm, that 5ppm input is not really going to have a huge impact on how much or how frequently you change water.

Think of it this way -- if you change at 20ppm, with 5ppm input water, and did a 50% water change, the new water is 12ppm, then goes up to 20 and change, etc.

If it was zero and you change at 20ppm, your new water after a 50% change is still 10ppm (vs 12ppm above). The input water makes a difference, but unless it is really high, it does not make that much of a difference. Increasing the percentage of change and the frequency of change has a much larger impact.

Now if the input is already 20ppm or something terrible, that's a different story, but that would be rare.

 

[jr125]

Thank you all. Your replies are certainly very educating. Yes, my tap water contains nitrates. And I know I'm overstocking my tank, and its not heavily planted enough to absorb all the nitrates. These factors combined are probably causing the nitrates to rise. And I wanted to counter that by using RO water which would contain zero nitrates.

However after reading your replies, I can see that I need to remineralize the water. And the flow is really very slow. I'm going to defer my RO purchase until I do more research about RO. Because I'm not a fan of remineralizing because its not practical for me. To do that, I need to mix the minerals into three large buckets, then siphon the water into my tank. Problem is my tank is already at shoulder height, and using siphon is quite a lot of work (to raise the bucket higher than the tank - oh boy)...

I didn't know there's a difference with RODI. I thought it came as a set of particle filter, carbon filter, and then RO membrane. I'll ask the LFS for more info too and educate myself, but as of now, I'm not too encouraged with using RO.

I started using RO water for changes for a variety of reasons. My water supplier seems determined to keep the PH very high, 8.5 or higher and it fluctuates seasonally. There is chlorine, chloramines, fluoride and a wide variety of other things I'd just as soon not have in my tank or deal with to eliminate/reduce.

I've never remineralized my stored RO water before adding to the tank at water change. I add 1/2 to 1 tsp of Equilibrium to the tank for about every 5 gals of plain RO water as I slowly add it. This maintains my tank at very close to 4DGH. I'm talking several hours for 40 gals or so in a 125gal tank. I've never had any problems doing it this way. I've tested GH during the process and it stays pretty consistent. I also add 1/2 tsp baking soda or Alkaline Buffer about 1/2 way through the water change and another when the tank is nearly full and this keeps my PH in the 6.4-6.6 range.

Since the Equilibrium contains quite a bit of potassium I skip the scheduled dose of that at water change time.

I store the RO water in empty ice cream pails I've collected over time(yum) and really only worry about water temp. If it's too cold in the winter I'll set the pails next to a heat vent to warm them up and then keep an eye on the water temp in the tank as I add new water. As I do this very slowly it really doesn't fluctuate much.

 

[Linwood]

I store the RO water in empty ice cream pails I've collected over time(yum) and really only worry about water temp.

And another great point about RO or RODI water... temperature equalization. For some the water coming out of a filter may be very cold, and need time to warm up. I have an extra heater I can through in the tank while it is building up, in that case (about 2 months per year; most times down here in Florida I have the reverse problem, and have to float some cold packs in it, or if I think about it early enough I freeze the first gallon or so and then add that back). Takes me most of a day to make 45 gallons, and I've had the water be as high as 88 when I brought it in to use.

 

[davido]

Here's a brief primer to help in your research.

The particulate filter takes out (usually) neutrally charged large particles like mud, rust, etc.

The carbon filter(s) will take out some chemicals, but in particular removes Chlorine from water treatment, which is harmful to the RO filter.

The RO filter will take out some percentage of most contaminants in the water, the percentage varying by temperature, pressure, and specific membrane. But for the sake of argument let's say 95% is removed.

Then, if you have one, the DI filter takes out negatively and positively charged ions in the water, hence "De-ionization". Most items going into solution do so by separating out into a negative and positive ion, and this electrical action to remove them takes out a large portion of the rest.

So say you start off with 100 TDS water after it gets through the carbon filters (and let's assume that is all in solution, i.e. "dissolve" solids). The RO filter then outputs water with 5 TDS, and then DI filter takes it to zero (OK, not precisely zero, but most aquarium quality meters will read zero after a DI filter).

If you start with 300 TDS water, RO might be 15, and RODI should still be zero. If it's 600, then RO may be 30, RODI is still zero.

This is why you will see some people use RO water without remineralization, depending on what they start with, and the quality of their filter -- it may actually be "mineralized" enough for them, if they are trying for water that is very, very soft. But it depends on the input water. If you start (as it sounds like you will be) with very low TDS to begin with, a RO filter (without DI) is still going to be darn close to zero.

Water that is too soft, i.e. near zero TDS, is not healthy for fish. It throws off the osmotic balance, in a loose sense sucking healthy stuff out of fish membranes (such flows usually go from high to low concentrations, which is why a RO filter is "reversed"). I have never seen any scientific study to say just how low is safe, but everyone seems to agree that zero is bad. If I were using RO water, with my 250 TDS input, I might not worry. If you are doing so with 60, my GUESS is you would be in the danger range without remineralization.

Now another common way RO or RODI water is used is dilution (someone around here had a signature saying "the solution to pollution is dilution" and that is very true). You can use 50/50 RO water with your tape water, to drop the TDS from 60 to 30 +/-. That works well when you are trying to reduce hardness, but it is marginally effective if your water is high in nitrates. By the way, how high? Is that really the issue?

A natural issue is "why RODI instead of RO" if it takes out 95% of the bad stuff. Well, many of us are a bit compulsive, and once you get all the way to RO you might as well get rid of it all and build your own water just how you want it. But that's not a necessity, but a choice.

Anyway...

Should you decide to do RO or RODI and remineralize, there are other solutions than siphoning. I got a big trashcan (Rubbermaid grey cans is frequently used and accepted as not introducing harmful chemicals). I then bought a pond pump. I toss it into the can to mix (it just swirls the water around). When the can is on a dolly. When I'm ready to put it in the tank, I roll it over, put a hose on the pond pump, and it let pump the water up into the tank. If you do this, you need to get a pond pump that has enough "head pressure" to raise the water to whatever height you need, plus a bit more to have good flow. Many will only go 3-5', some 7-9'. Another alternative if you are handy is a bilge pump - they pump much higher, but cost more, and need 12v power -- I use that as I am moving a lot of water and just plug it into a transformer I got with LED lights. What I did was put a piece of PVC on the end, cap it off, and drill a bunch of holes in it so I get more of a spray when the water comes out than a stream, to keep from disturbing the tank so much.

But... back to the "solution to pollution is dilution"....

If you are over stocked, and building up nitrates, even if your input water has some (let's say 5ppm), the simpler answer is probably to change water more aggressively. If you are changing at 40ppm or even 20ppm, that 5ppm input is not really going to have a huge impact on how much or how frequently you change water.

Think of it this way -- if you change at 20ppm, with 5ppm input water, and did a 50% water change, the new water is 12ppm, then goes up to 20 and change, etc.

If it was zero and you change at 20ppm, your new water after a 50% change is still 10ppm (vs 12ppm above). The input water makes a difference, but unless it is really high, it does not make that much of a difference. Increasing the percentage of change and the frequency of change has a much larger impact.

Now if the input is already 20ppm or something terrible, that's a different story, but that would be rare.

Thank you. +1
Very good explanation on the RO. I guess DI is not necessary for me. And a 50-50 mix may be more ideal for my case.

My tap water nitrates is indeed between 10-20ppm. And I change only 30% water due to shrimps.

 

[Linwood]

My tap water nitrates is indeed between 10-20ppm. And I change only 30% water due to shrimps.

If that's a real value I would complain, 10ppm is the limit for safe drinking water from the EPA. Also, if you have that high of nitrates, have you checked nitrites, which may be even more damaging to your aquarium?