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Discussion Starter · #1 ·
Hi everyone,



I’m considering switching over to RO water, and have a few questions I’m hoping you can all answer. A few things that I feel will be relevant:



  • I change about 75 gallons of water per week in a 125g tank. This would leave 50 gallons of water left, but a lot of that is taken up by substrate and hardscape. I genuinely have no idea how much water that displaces, so an accurate percentage of water changed is hard to give. My journal is in my signature so you can see the amount of hardscape we’re talking about.
  • I have about 180 lbs of Seiryu stone in my tank, along with pretty high CO2. This leeches a ton of Ca and Kh.


Here are my questions:



If I go forward with RO water, I’ll need more than 55 gallons of water storage. I’ve found a tall, narrow storage tank that will hold 80 gallons of water, but the top is somewhat closed and there is a bulkhead near the bottom to connect a pump. I know that I should remineralize before pumping the water back to the tank, but my problem is that I’ll never be able to pump 100% of the storage tank out. After the first water change, how would I go about figuring out how much Ca and Mg to add to the new RO water? Would I need to calculate how much water was pumped, and change the amount of Ca and Mg I add each and every time? This feels both tedious, and prone to miscalculation.



Second question… With the rocks that I have leeching a ton of Ca, the water hardness rises a not-insignificant amount every week. When I do my water change, there is going to be a huge drop in hardness. Could this dangerous to the fauna? I don’t know exactly how much Gh and Kh leeches during the week, so I’m not really able to give exact numbers. What I do know is that my TDS currently goes up about 100 points during the week. This obviously includes fertilizers and dissolved organics, but a lot of it is hardness and Kh.



If I make the change to RO water, will the rocks leech even more hardness than they currently do, or will that not make a big difference?
 

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That Seiryu stone is a real wild card. It’s counter intuitive to the advantages of going with RO water. We go with RO to have very low dKH and to be able to control every variable. The stones will be fighting that.

Keep mind that Seiryu was popularized by the ADA style, but those tanks all have an active substrate like Amazonian, which counters the effect of the stone and keeps dKH low.

As to RO storage, mine is stored in two 55G drums that are tied to each other. I change 70 gallons at a time, then dose the new 70 gallons to my target, so the RO water waiting for use always has the same mineralization and macro dosing. It’s really very easy. I have my tank marked so that I drain the tank to the same level every time.

Furniture Dishware White Table Bathroom sink


To figure out how many gallons you are removing, you can get something like an Orbit water flow meter, or drain to 5G buckets one time to get a measurement, or just calculate the best you can. The key is keeping the water change consistent, that way you know your dosing is consistent.

In the end, you really need to consider your objectives. If you plan on keeping easier plants and don’t plan on adding sensitive harder to grow species, RO + the stone will work fine. You’ll be somewhat limited in selection as certain plants really need low KH, but that is a small subset of plants. If your goal is to expand your horizons and get more plant centric with your display, in the long run you’d be better off without the stone.
 

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Discussion Starter · #3 ·
That Seiryu stone is a real wild card. It’s counter intuitive to the advantages of going with RO water. We go with RO to have very low dKH and to be able to control every variable. The stones will be fighting that.

Keep mind that Seiryu was popularized by the ADA style, but those tanks all have an active substrate like Amazonian, which counters the effect of the stone and keeps dKH low.

As to RO storage, mine in stored in two 55G drums that are tied to each other. I change 70 gallons at a time, then dose the new 70 gallons to my target, so the RO water waiting for use always has the same mineralization and macro dosing. It’s really very easy. I have my tank marked so that I drain the tank to the same level every time.

View attachment 1025987

To figure out how many gallons you are removing, you can get something like an Orbit water flow meter, or drain to 5G buckets one time to get a measurement, or just calculate the best you can. The key is keeping the water change consistent, that way you know your dosing is consistent.

In the end, you really need to consider your objectives. If you plan on keeping easier plants and don’t plan on adding sensitive harder to grow species, RO + the stone will work fine. You’ll be somewhat limited in selection as certain plants really need low KH, but that is a small subset of plants. If your goal is to expand your horizons and get more plant centric with your display, in the long run you’d be better off without the stone.
Thank you Gregg. How will the Gh reduction during a water change affect the fish? Could the stone leech so much hardness that a water change with remineralized RO could be dangerous?
 

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Looks like Gregg beat me to the reply on the tanks - a pair of 55g drums side by side would be your best option if you have the room.
"I know that I should remineralize before pumping the water back to the tank, but my problem is that I’ll never be able to pump 100% of the storage tank out." - For me, I use the same drum for my 40g & 20g on Saturday and my 75g on Sunday. With that said, the starting level of RO in my drum is always different. If you have a TDS meter, then it is really easy to calculate out how much Ca, Mg, etc to add back in. I have also gotten very good at "stirring" my drum for faster dissolving (more on that if you are interested).
"What I do know is that my TDS currently goes up about 100 points during the week." Ok, so you do have a TDS meter - thats good. Now - WOW that is a big rise in TDS. My crazy setup is (90ppm after a water change, 105ppm after I add ferts, and about 110ppm at the end of the week just before water change. A little mathmatical fun...
Assuming your Seiryu stone is leaching just Ca, it would take about 40 ppm of CaSO4.2H2O to generate a swing of 5.5968 dGH. 5.5968 * 17.86 equals about 100ppm TDS.
Granted, as you said, the 100ppm TDS includes other things, but this gives you a better idea how much CA "could" be added to the water column.
Math stuff I know - guessing the best approach to make things better.... yeah, question best left to others. If the Seiryu stone really does leach a large amount of Ca - would it make sense to add 15-20ppm Mg to the RO water and thats it?? No Ca and no K2CO3??
 
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You wont regret it but do yourself a favor and purchase a 25ft hose to come from your RO unit straight into whatever tank your filling. I used to "cure" water as I remineralized it in a storage but with the fish I have its no problem to remineralize it as it fills as its basically a drip acclimation anyways (200 gpd). Breeding guppies & endlers so maybe thats why I can get away with it.
 

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Discussion Starter · #7 ·
Math stuff I know - guessing the best approach to make things better.... yeah, question best left to others. If the Seiryu stone really does leach a large amount of Ca - would it make sense to add 15-20ppm Mg to the RO water and thats it?? No Ca and no K2CO3??
I was actually considering this, but figured it would be too drastic of a change for the fauna.
 

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You wont regret it but do yourself a favor and purchase a 25ft hose to come from your RO unit straight into whatever tank your filling. I used to "cure" water as I remineralized it in a storage but with the fish I have its no problem to remineralize it as it fills as its basically a drip acclimation anyways (200 gpd). Breeding guppies & endlers so maybe thats why I can get away with it.
@jellopuddinpop doesn't need a 25 foot hose. He has a sink behind a wall right next to his built-in tank. His setup is awesome. I haul water in 5 gallon bottles and buckets. Maybe I'll get a Python.
 

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Discussion Starter · #9 ·
@jellopuddinpop doesn't need a 25 foot hose. He has a sink behind a wall right next to his built-in tank. His setup is awesome. I haul water in 5 gallon bottles and buckets. Maybe I'll get a Python.
I'm the poster child for "technology doesn't guarantee things will be easy" lol.

It was definitely helpful to plan construction around a built in tank. I told my wife that I didn't want the responsibility of having a tank that 100% needed to be maintained unless I had free reign over what happened behind the scenes. When you construct the foyer with a bigg a$$ hole in the wall for a tank, there's no going back lol.
 

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Maybe an old time water changer that you clip onto the side of your tank. I first saw it in an old Axlerod book from the Sixties. It slowly changes your water over time. Only instead of using tap water (which @jellopuddinpop can't do because his tap water isn't good,) he would find a way to slowly add RO water. His Seiryu stone would dose his CaCO3 at a yet to be determined rate. He would adjust the rate of water changing to keep the CaCO3 where he wants it. MgSO4 dosing would depend on plant uptake and desired Ca to Mg ratio which could eventually be estimated. The slow rate of the water changing would prevent osmotic shock to the animals. All in the realm of theory of course. The reality would be hard to realize.
 

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Discussion Starter · #11 ·
Maybe an old time water changer that you clip onto the side of your tank. I first saw it in an old Axlerod book from the Sixties. It slowly changes your water over time. Only instead of using tap water (which @jellopuddinpop can't do because his tap water isn't good,) he would find a way to slowly add RO water. His Seiryu stone would dose his CaCO3 at a yet to be determined rate. He would adjust the rate of water changing to keep the CaCO3 where he wants it. MgSO4 dosing would depend on plant uptake and desired Ca to Mg ratio which could eventually be estimated. The slow rate of the water changing would prevent osmotic shock to the animals. All in the realm of theory of course. The reality would be hard to realize.
My big hurdle right now, is there's no simple way to get a reliable Ca measurement from the water. All of the tests out there are designed for salt water, where they are measuring in the hundreds of ppm vs tens. If I could know exactly how much Ca was leeching, I could account for that with RO in my water changes.

I was just thinking about it, and maybe I don't need to know exactly how much Ca the stones leech. I should be able to let the plants tell me.

I change out just about 70 gallons of water a week, so I can dose that water to like 5ppm Mg with MgSO4 only (going to call this RO water). Each week, I use 10% more RO water, so I get a slow changeover. After 10 weeks, I'll be changing with 100% RO water. If at any point during this process I see a Ca deficiency, then I know I need to add some Ca to the RO water. As long as there's not going to be an osmotic shock to the fish during a water change, I'm really only worried about adding enough hardness for the plants to survive.

I was never planning on adding K2CO3, because the stones will leech enough to keep my ph from crashing. Lots of people run with 0 Kh, so I'm not concerned about that.

Does this seem like it would work?
 

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I was just thinking about it, and maybe I don't need to know exactly how much Ca the stones leech. I should be able to let the plants tell me.

I change out just about 70 gallons of water a week, so I can dose that water to like 5ppm Mg with MgSO4 only (going to call this RO water). Each week, I use 10% more RO water, so I get a slow changeover. After 10 weeks, I'll be changing with 100% RO water. If at any point during this process I see a Ca deficiency, then I know I need to add some Ca to the RO water. As long as there's not going to be an osmotic shock to the fish during a water change, I'm really only worried about adding enough hardness for the plants to survive.

I was never planning on adding K2CO3, because the stones will leech enough to keep my ph from crashing. Lots of people run with 0 Kh, so I'm not concerned about that.

Does this seem like it would work?
Yes, that will work.

And I would not be worried about changing Ca levels as far as fish go. They could pretty much care less.

The Ca kits are designed for salt water, but work fine for our use. They are measuring a much higher number, so we just have to adjust the methodology. Here is the way to use the Ca kit to get readings for our levels of Ca.

20 ml of aquarium water
Add 5 drops of #1 solution and mix.
Add 1 drop of #2 solution, mix and look for color change from pink to blue. Each drop of #2 solution equals 5 ppm Ca.

Once you know Ca, you can calculate for Mg. Here is the formula.

((17.86 x dGH) - (2.5 x Ca ppm)) / 4.1 = Mg ppm

Hope that helps.
 

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The above methodology works very well. Something to add - use a glass container to hold the 20ml of aquarium water. A taller/skinnier container is better than a shorter/fatter container. Place the container on a very white surface and look down from the top to see the color change.
 

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Discussion Starter · #14 ·
I could start tracking this today with my water change. I'll check the Ca before and after the water change each week for a month or so, and should be able to see how much Ca is leeching from the rocks.

This will also tell me how much "other" is in my TDS increase.

Yes, that will work.

And I would not be worried about changing Ca levels as far as fish go. They could pretty much care less.

The Ca kits are designed for salt water, but work fine for our use. They are measuring a much higher number, so we just have to adjust the methodology. Here is the way to use the Ca kit to get readings for our levels of Ca.

20 ml of aquarium water
Add 5 drops of #1 solution and mix.
Add 1 drop of #2 solution, mix and look for color change from pink to blue. Each drop of #2 solution equals 5 ppm Ca.

Once you know Ca, you can calculate for Mg. Here is the formula.

((17.86 x dGH) - (2.5 x Ca ppm)) / 4.1 = Mg ppm

Hope that helps.
Thank you Gregg. Will this work with the Fluval test as well, or is this specifically for the API test?

Fluval Fresh/Salt Calcium Test Kit, 3.5" L X 5.5" W X 2" H | Petco

API Aquarium Calcium Test Kit | Petco
 

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Thank you Gregg. Will this work with the Fluval test as well, or is this specifically for the API test?

Fluval Fresh/Salt Calcium Test Kit, 3.5" L X 5.5" W X 2" H | Petco

API Aquarium Calcium Test Kit | Petco
That's for the API test. But I assume it would be similar for the Fluval. In each case their intention is to measure much higher Ca values than we have in our fresh water systems, so some adjustment is needed.

I'll look at the Fluval later tonight and let you know if I can figure an equivalent way to use it.
 

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My big hurdle right now, is there's no simple way to get a reliable Ca measurement from the water. All of the tests out there are designed for salt water, where they are measuring in the hundreds of ppm vs tens. If I could know exactly how much Ca was leeching, I could account for that with RO in my water changes.
Here is a link for a test that might work: Calcium, Magnesium & Total Hardness Test Kit The test resolution is 4 ppm. You can dilute the sample to get a higher range out of the test.
 

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Discussion Starter · #17 ·

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Yes, that will work.

And I would not be worried about changing Ca levels as far as fish go. They could pretty much care less.

The Ca kits are designed for salt water, but work fine for our use. They are measuring a much higher number, so we just have to adjust the methodology. Here is the way to use the Ca kit to get readings for our levels of Ca.

20 ml of aquarium water
Add 5 drops of #1 solution and mix.
Add 1 drop of #2 solution, mix and look for color change from pink to blue. Each drop of #2 solution equals 5 ppm Ca.

Once you know Ca, you can calculate for Mg. Here is the formula.

((17.86 x dGH) - (2.5 x Ca ppm)) / 4.1 = Mg ppm

Hope that helps.
Hope to get any idea. Today I prepared a 10L stock with
CaSO4.2H2O
K2SO4
MgSO4.7H2O
KHCO3

Total target ppm was 155 but it comes 200ppm

Two major issues observed if I am correct

1. Scale precision 0.1g
2. Commercial grade elements.
But happy atleast it comes 200PPM
Any thought?
 

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Hope to get any idea. Today I prepared a 10L stock with
CaSO4.2H2O
K2SO4
MgSO4.7H2O
KHCO3

Total target ppm was 155 but it comes 200ppm

Two major issues observed if I am correct

1. Scale precision 0.1g
2. Commercial grade elements.
But happy atleast it comes 200PPM
Any thought?
You can buy a reference weight for calibrating scales. You want one that's kind of close to the limit of the scale. For example the scale I have can weigh 220 grams. The calibrating weight that came with it is 200 grams. You put the weight on the scale and divide what it weighs by what it should weigh. Then when you weigh your fertilizer you divide the weight of the fertilizer by the percentage your scale is off by and add more or less fertilizer accordingly. I don't know for a fact if this actually works. It's just an idea I came up with.
 

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You can buy a reference weight for calibrating scales. You want one that's kind of close to the limit of the scale. For example the scale I have can weigh 220 grams. The calibrating weight that came with it is 200 grams. You put the weight on the scale and divide what it weighs by what it should weigh. Then when you weigh your fertilizer you divide the weight of the fertilizer by the percentage your scale is off by and add more or less fertilizer accordingly. I don't know for a fact if this actually works. It's just an idea I came up with.
Thanks
 
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