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Should peat be under the substrate or in the filter also is there a different between ro and ro/di ?

anewbie

Well-Known Member
Messages
1,399
I've mentioned that i'm setting up a large tank this spring - i will use pure ro wter but i'm unsure if it matters if the peat is under the substrate or in the filter. My hope is i can put it in the filter (in filter bag) so it is easy to replace as needed.

Conversely is there a difference between ro unit that say 'ro' and those that say 'rodi'; is ro implying di ? Again any suggestion around optimization for this application. As for ro unit i'm looking at:
(it has good volume per day and effiicency is stated 1:1 - he says this is the unit he uses for his fertlizer and claims it is 99%)

Another unit i found is

But it is quite expensive (it states di and is 1:1 waste but very costly).
-
Given the volume of water required I need at least 200 gpd and want waste no worse than 1:1 - for water change i'll probably have to use acid to lower the new water ph to the tank's ph and the peat would be use more for stability with leaves of course.
 

Ben Rhau

Apisto Club
Messages
571
Location
San Francisco
I've mentioned that i'm setting up a large tank this spring - i will use pure ro wter but i'm unsure if it matters if the peat is under the substrate or in the filter. My hope is i can put it in the filter (in filter bag) so it is easy to replace as needed.
The way peat works is by ion exchange. Since the ions disperse freely throughout the water, I see no reason it would need to be under the substrate. The reason some people put it under the substrate is to prevent the peat from floating everywhere. If you do that, it's much harder to replenish the peat once all of the exchange sites are occupied.

Conversely is there a difference between ro unit that say 'ro' and those that say 'rodi'; is ro implying di ? Again any suggestion around optimization for this application. As for ro unit i'm looking at:
RODI units include a DI stage. That's needed if you want TDS zero. If you just want low TDS, you don't need DI. I will add, however, that the DI stage is very effective at removing chloramine.

But it is quite expensive (it states di and is 1:1 waste but very costly).

Spectrapure makes very high quality gear, but as you say it's quite expensive. I recommend Buckeye Hydro, which tends to sell higher end cartridges at a lower price point. They aren't configured to be 1:1 out of the box, but since all the parts are more or less the same, you can choose to plumb it the same way as the other two configurations you shared.

-B
 

anewbie

Well-Known Member
Messages
1,399
The way peat works is by ion exchange. Since the ions disperse freely throughout the water, I see no reason it would need to be under the substrate. The reason some people put it under the substrate is to prevent the peat from floating everywhere. If you do that, it's much harder to replenish the peat once all of the exchange sites are occupied.


RODI units include a DI stage. That's needed if you want TDS zero. If you just want low TDS, you don't need DI. I will add, however, that the DI stage is very effective at removing chloramine.



Spectrapure makes very high quality gear, but as you say it's quite expensive. I recommend Buckeye Hydro, which tends to sell higher end cartridges at a lower price point. They aren't configured to be 1:1 out of the box, but since all the parts are more or less the same, you can choose to plumb it the same way as the other two configurations you shared.

-B
Thanks. I guess for low ph tank i want tds zero - well maybe not - is the tds left behind kh or gh - i presume gh so maybe that is useful for plants? We have chlorine here - definitely not chloramine though there is nothing to stop the city from changing i don't expect it.

I checked buck-eye but they top out at 150 gpd; and while I think 200 might be ok that is sort of a bare min.

Do I really need the 'di'; the nilgoc ticks all my boxes with regards of 600 gpd; 1:1 waste and he claims it has work well over a year per filter set (my base water has lower tds than his).
 

Ben Rhau

Apisto Club
Messages
571
Location
San Francisco
Thanks. I guess for low ph tank i want tds zero - well maybe not - is the tds left behind kh or gh - i presume gh so maybe that is useful for plants? We have chlorine here - definitely not chloramine though there is nothing to stop the city from changing i don't expect it.
TDS is a misnomer the way we use it. It just stands for "total dissolved solids." But that's not actually accurate. A TDS meter measures electroconductivity (EC) which is the presence of ions in solution. We use a crude conversion, multiplying the conductivity by a number (for freshwater, 0.5 or 0.64) to back out an estimate of TDS in parts per million. This does not distinguish between the types of ions that contribute to KH or GH, and also doesn't include dissolved substances that aren't ions. That said, TDS is a quite useful tool for aquarists, as it gives us an understanding of the osmolarity of the water.

So, to answer your question, what is left behind? It depends on the membrane whether it prefers to exclude one type of ion vs another. LIkely, Instead of rejecting 100% of one type and 0% of another, it's a probability distribution for each. My guess is very small and singly charged ions are more likely to get through.

I would think that even if your TDS was 30 or 40 coming out, your GH and KH would be unmeasurable with a standard kit. If your starting TDS is already low, it will probably be below 10 after RO.

Do I really need the 'di'; the nilgoc ticks all my boxes with regards of 600 gpd; 1:1 waste and he claims it has work well over a year per filter set (my base water has lower tds than his).

Assuming you have a very low TDS after the RO stage, the DI stage will remove everything else. However, unless you are working with extreme blackwater fish (like Parosphromenus) or saltwater, you don't need DI. Most of the folks on this forum use RO only, and are fine with the residual electroconductivity. The don't mind adding a bit of dechlorinator afterward. Or simply aging it, if it's just chlorine.

Do I really need the 'di'; the nilgoc ticks all my boxes with regards of 600 gpd; 1:1 waste and he claims it has work well over a year per filter set (my base water has lower tds than his).

As I said before, I'm skeptical that you can get 1:1 without some kind of compromise, likely needing to exchange the medium and/or membrane frequently. But I understand your constraints, as you have very high volumes of water.

I don't think you need DI, but if it only comes with a DI stage, your choices are:
  1. Use it anyway, since it doesn't hurt to have less in your water
  2. Bypass the DI stage. You're also not required to replace the DI column after it's exhausted if you don't need that level of filtration. I would still bypass it in that case.
Cheers
 
Last edited:

anewbie

Well-Known Member
Messages
1,399
TDS is a misnomer the way we use it. It just stands for "total dissolved solids." But that's not actually accurate. A TDS meter measures electroconductivity (EC) which is the presence of ions in solution. We use a crude conversion, multiplying the conductivity by a number (for freshwater, 0.5 or 0.64) to back out an estimate of TDS in parts per million. This does not distinguish between the types of ions that contribute to KH or GH, and also doesn't include dissolved substances that aren't ions. That said, TDS is a quite useful tool for aquarists, as it gives us an understanding of the osmolarity of the water.

So, to answer your question, what is left behind? It depends on the membrane whether it prefers to exclude one type of ion vs another. LIkely, Instead of rejecting 100% of one type and 0% of another, it's a probability distribution for each. My guess is very small ions are more likely to get through.

I would think that even if your TDS was 30 or 40 coming out, your GH and KH would be unmeasurable with a standard kit. If your starting TDS is already low, it will probably be below 10 after RO.



Assuming you have a very low TDS after the RO stage, the DI stage will remove everything else. However, unless you are working with extreme blackwater fish (like Parosphromenus) or saltwater, you don't need DI. Most of the folks on this forum use RO only, and are fine with the residual electroconductivity. The don't mind adding a bit of dechlorinator afterward. Or simply aging it, if it's just chlorine.



As I said before, I'm skeptical that you can get 1:1 without some kind of compromise, likely needing to exchange the medium and/or membrane frequently. But I understand your constraints, as you have very high volumes of water.

I don't think you need DI, but if it only comes with a DI stage, your choices are:
  1. Use it anyway, since it doesn't hurt to have less in your water
  2. Bypass the DI stage. You're also not required to replace the DI column after it's exhausted if you don't need that level of filtration. I would still bypass it in that case.
Cheers
A few data points - nilogc base tds is around 60 and his output is around 5 from this unit. My base tds is around 120 so it might be quite a bit higher (i guess that also depends what is in the water - he said his water had a lot of iron - mine has a lot of limestone). He indicated his cartridge has lasted over 2 years - that should be more linear for me so i should get at least a year. Hum.
-
Oh well - hate to waste money but i could start with it and then go with a more expensive unit if need be.
 

Ben Rhau

Apisto Club
Messages
571
Location
San Francisco
A few data points - nilogc base tds is around 60 and his output is around 5 from this unit. My base tds is around 120 so it might be quite a bit higher (i guess that also depends what is in the water - he said his water had a lot of iron - mine has a lot of limestone).
For reference, my tap water varies between 20 and 80 TDS depending on time of year. The TDS after the RO stage is usually around 1 or 2 regardless. Same might be true in your case, where 60 and 120 aren't that different.

He indicated his cartridge has lasted over 2 years - that should be more linear for me so i should get at least a year. Hum.
It's a function of volume, not time.
 

MacZ

Well-Known Member
Messages
3,050
Location
Germany
For reference, my tap water varies between 20 and 80 TDS depending on time of year. The TDS after the RO stage is usually around 1 or 2 regardless. Same might be true in your case, where 60 and 120 aren't that different.
Another reference: My tap has about 180mg/l TDS, the result from the RO is 5-6.

However, unless you are working with extreme blackwater fish (like Parosphromenus) or saltwater, you don't need DI.
Fully agree.

My guess is very small and singly charged ions are more likely to get through.
Natrium, copper and chlorine get through, although only residual amounts if the activated carbon stage is working correctly. That stage should also remove chloramine. Luckily in most of continental Europe the tap is not chlorinated at all, or rather the stuff has to be removed before being send into the public system.
Copper I tested actually, as we have copper plumbing in this house and I was curious why catfish tend to not survive in my tanks and those of one of my neighbours. Result was a reduction of less than 40% of the copper ions. As I have no way of removing it without getting an extra DI stage I simply don't keep catfish. It's the easier way for me.
 

MacZ

Well-Known Member
Messages
3,050
Location
Germany
And for the original question about where to position the peat: Put it in a media bag and just put it in the tank somewhere behind the scape.
 

anewbie

Well-Known Member
Messages
1,399
One thing I should have mentioned is that i'm prefiltering the water - i.e,

water heater -> carbon filter -> carbon filter -> ro unit

(the carbon filters are just giant thingy filled with carbon - i'm using two of them in serial as paranoia).
 

Apistoguy52

Active Member
Messages
295
I approve of the extra carbon. Chlorine kills fish, chlorine kills membranes. I run big carbon tank, sediment, carbon block, carbon block before it ever sees the carbon block of the RO filter BAC548AF-868F-4799-A601-1C20B8516BF9.jpeg
 

Apistoguy52

Active Member
Messages
295
Years ago I accidentally bypassed the carbon stages before my membrane…one 8 hour run of .5ppm free chlorine was enough to increase the TDS of the permeate water from 1ppm tds to 30 ppm tds
 

Ben Rhau

Apisto Club
Messages
571
Location
San Francisco
Yikes! I don’t think it would be possible for me to do that based on the plumbing (though I can make many other kinds of mistakes). But I can understand how that would make you extra cautious.
 

Apistoguy52

Active Member
Messages
295
Yikes! I don’t think it would be possible for me to do that based on the plumbing (though I can make many other kinds of mistakes). But I can understand how that would make you extra cautious.
Yeah, @400 a membrane, it’s a mistake I would prefer not to make again. Suppose I deserved it. Drinking and tank maintenance don’t mix
 

anewbie

Well-Known Member
Messages
1,399
Both RO units you’re considering include two carbon block stages. Don’t overthink this.
I left out a detail - it is actually:
heater -> temp control value -> carbon filter -> carbon filter -/> split -> ro unit; -> available for aquariums
-
Not all my aquariums will get pure ro water - also i figure i would let the carbon filter in the ro unit exhaust. The vendor for the carbon filter estimate they will last 5ish years since they are designed for whole house filtered water and i'm only using them with the aquariums but i'll probably cycle them and replace the carbon every couple of years.
 

Apistoguy52

Active Member
Messages
295
I wish i lived in the north west where they have like 30 tds out of the faucet.
No, you really don’t. pH drift gets a little crazy if you aren’t on your A game.
 

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