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RO water - is remineralizer required?

illumnae

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5 Year Member
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68
I'm in the midst of resetting my 600 gallon tank, moving back to South American cichlids after 2 years of dabbling with Tanganyikans. I have an auto water change system set up that changes about 5% - 8% of water daily using RO water. Several years ago when utilizing this system (without remineralizing or using botanicals), my tank settled at pH 3.7 without any noticeable pH swings (I use a Neptune Apex system to monitor pH, temperature and conductivity 24/7). Conductivity was high at about 200 µS/cm but I tended to overstock so I think most of that was nitrates. In that tank I was able to keep the most sensitive of wildcaught blackwater species (Uaru fernandezyepezi, Pterophyllum altum, Crenicichla multispinosa, etc) but some species with more moderate requirements didn't do so well - I suspect due to lack of gH and other minerals. I'm hoping to keep a mix of blackwater and clearwater species this time around, and I fully intend to utilize botanicals for at least a slight tint in the water. I will also have hardy plants like java fern and anubias as part of the scape, and may utilize co2 during lighted hours. I'm hoping this time to maintain pH stable between 5-6. I have a dosing pump set up and will be dosing a diy concentrated tannin solution daily to replenish what's being removed by the auto water changes (though I have no idea how much to dose daily to be honest!). The dosing pump will be able to dose gH and kH liquids as required (it's how I kept my gH and kH high for my Tanganyikan fish). Should I be remineralizing my water with such liquids and if so, what gH and kH values should I be aiming for to keep my pH stable between 5-6 and my fish healthy?
 

MacZ

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Unadulterated RO is completely fine as a base, add humic substances and that is all you have to do. If you look at water parameters from South America:


You will soon notice: Except coastal waters on the Atlantic, Main channels of bigger rivers and some hillstreams from the Andes, basically all bodies of freshwater in South America are still categorized as softwater (EC < 50µS/cm). This means whatever you want to keep, as long as it comes from smaller rivers, creeks, lakes etc. will likely be completely content with GH not measurable. All of these fish take the electrolytes and nutrients they need completely from their food and are well equipped to retain this against the osmotic pressure in soft water. So I don't see a problem on that side.

Now for KH. Softwater obviously also has no noteworthy KH. But one doesn't need it. While in blackwater the humic substances are buffering as well, producing pH values between 4 and 6, clearwater simply also lacks the H+ ions necessary to lower pH.

Now thirdly, I want to get you away from the use of CO2 in softwater. The balance of CO2, KH and pH works differently without KH, the system is quite unstable. Also considering your plant plans it is overkill. I rather recommend fast growing plants. Nymphaea, Hydrocotyle, all kinds of floaters or stem plants (like Myriophyllum or Cabomba) that can be left floating aswell as emersed plants like Epipremnum, Monstera and the like, are what you want for such a tank. They all can use the part of the tank that actually gets enough light and they can cheat by using atmospheric CO2.

And ultimately: I would pretreat the water with humic substances before leading it into the tank. And I'd also recommend cultivating a good layer of botanical mulm, by regularly adding leaves. Otherwise you wash out almost all the humic substances pretty quickly.

To be honest... a well seasoned softwater system with established mulm and leaf layers, plants that are good at extracting lots of nutrients efficiently and a reliable filter will at one point only require addition of untreated RO to make up for evaporation.
 

illumnae

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5 Year Member
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68
I can understand the desire to replicate natural water conditions as much as possible. I have always tried to do so myself. However for this tank I'm honestly trying to go with a no hassle automated setup. I'm getting old and I'm tired and trying to replicate natural water conditions gives me alot of limitations that are frankly hard to implement in such a large tank because tannins are such an inconsistent and unmeasurable component of the system. To do an automatic water change I just drip water in 24/7 from my RO barrel that is also automatically topped off via my 400gpd RO system and a float switch. To dose gh and kh back into the water is as simple as dissolving x powder into y litres of water and setting my dosing pump to dose z ml of liquid a day. How do I keep tannins constant automatically? Do I boil 20 large leaves and then dose the resulting liquid? How much do I dose? How often?

Also, I really do want a simple planted tank with CO2 and as you have noted, a true blackwater setup is not conducive for that. So I will have a flooded forest look to the tank with a slight tint from the botanicals that I do put in, but the botanicals are meant to serve only as an aesthetic decoration and not a water conditioner. I want the "plants" portion of the "forest" theme to take precedence in this tank. With this in mind, while I know the fish will thrive more in a blackwater setup, I would rather this tank be a more balanced type of setup to suit both fish and plants, and also keeping in mind that I may be keeping fish that are not strictly from blackwater rivers or streams too (e.g. blue/brown discus come from clearwater rivers and lakes).

With the above in mind, what would be the recommended gh and kh I should be aiming for to be able to maintain such conditions in my tank (with pH stabilizing at or below 6.0)?

P.S. I still do intend to continue keeping blackwater tanks, but for my smaller dwarf cichlid tanks. Here's a 20 gallon custom tank that I am keeping in my office. It currently houses red crystal tetras, tucano tetras and zebra otos. I haven't decided which dwarf cichlids to bring from home to house there yet.
 

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MacZ

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If it's ok I'll come back to you on Tuesday. I'm on a trip over a long weekend.
 

illumnae

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5 Year Member
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68
Please enjoy your trip fully! Im not in a huge rush, and you definitely do not owe me an answer!
 

MacZ

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2,984
Location
Germany
To do an automatic water change I just drip water in 24/7 from my RO barrel that is also automatically topped off via my 400gpd RO system and a float switch. To dose gh and kh back into the water is as simple as dissolving x powder into y litres of water and setting my dosing pump to dose z ml of liquid a day. How do I keep tannins constant automatically? Do I boil 20 large leaves and then dose the resulting liquid? How much do I dose? How often?
Ok, I see now how your change-system works. The addition of GH/KH is, as established, not necessary unless you want CO2 (see below). So you can technically forgo on that and safe the money.
Now about the humic substances: There is no numerical consistency with natural products. Leaves and botanicals contain varying amounts. BUT the trick is not to have a certain colour of the water but some tint. Be it strong or weak (in tea terms) is not important, you can't overdose and barely underdose if the stuff is visible. If you aerate the barrel you can just add the leaves directly or brew them over so they sink and add them to it with the "tea". Do that regularly (once every 2 weeks) with a strong source of it, like catappa leaves and that's it.
Then add additional botanicals to the tank itself and that's all you have to do. You only might have to fine tune the amount of water that goes through the system to fewer liters / day.

That would be it if you went for true softwater. Not blackwater. I think that's where you lost me perhaps.
You can barely recreate THAT in a tank. I struggle keeping the EC down as anybody else. And the parameters are on the brink between clear- and blackwater. The difference is not a lot. True blackwater has an EC below 10µS/cm and pH is under 5.5, while in clearwater EC is at 15-20µS/cm and pH under 6. That's all for the measurable parts. Of course blackwater is also heavily tinted, but clearwater can be quite dark, too.

Also, I really do want a simple planted tank with CO2 and as you have noted, a true blackwater setup is not conducive for that. So I will have a flooded forest look to the tank with a slight tint from the botanicals that I do put in, but the botanicals are meant to serve only as an aesthetic decoration and not a water conditioner. I want the "plants" portion of the "forest" theme to take precedence in this tank. With this in mind, while I know the fish will thrive more in a blackwater setup, I would rather this tank be a more balanced type of setup to suit both fish and plants, and also keeping in mind that I may be keeping fish that are not strictly from blackwater rivers or streams too (e.g. blue/brown discus come from clearwater rivers and lakes).
I still have problems wrapping my head around it why you would still want CO2 injection.
You would only add remineralization to make the system CO2 safe. Nothing else. I mean there is no other reason than that. Because this kind of setup is also possible without. CO2 injection is in most cases only a given in a very brightly lit environment and also requires tons of fertilizers that would drive up EC even further. CO2-injection basically pushes you into high tech scaping, which will use up resources, high maintenance and strict observation. I might also add: With that waterchange system you also remove lots of dissolved CO2. So you add CO2, add minerals, add fertilizers... and so on.
If you want just true clearwater, it's just as described above.
With the above in mind, what would be the recommended gh and kh I should be aiming for to be able to maintain such conditions in my tank (with pH stabilizing at or below 6.0)?
pH would not be stable at all, and couldn't be stabilized. Better forget anything about trying to keep pH stable. CO2, even with KH, will lower it by day and when it's off by night the pH will rise. That's because the three values are continuously balancing each other out. You raise CO2, pH drops and temporarily KH as well. You raise KH, pH rises. You lower pH by other means than CO2, KH drops and CO2 drops. I know the principles.
Btw: GH is not important for that equation except the fact that KH is part of GH in natural systems.

But I have to admit: I haven't used CO2 in any tank besides for experimentation on water parameters and I am specialized on softwater systems. To me what you want is going to be a labourous Sisyphos task and from what I've seen others do, I'm curious how long you will keep up with it before you switch for full remineralization for a typical South American community with a tapwater (-like) base or quit CO2.
I'm not trying to be snarky here, it's just that I've seen people try and fail doing the splits on this over and over again. I don't want to promise wonders where I don't see them happening.
P.S. I still do intend to continue keeping blackwater tanks, but for my smaller dwarf cichlid tanks. Here's a 20 gallon custom tank that I am keeping in my office. It currently houses red crystal tetras, tucano tetras and zebra otos. I haven't decided which dwarf cichlids to bring from home to house there yet.
Nice tank... I'd probably just do a single male. After all, it's a display and with the tankmates probably the best choice.
Hope you can bring down the current significantly, because except the O. cocama none of the fish will like strong currents.
 

illumnae

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5 Year Member
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68
Thank you so much for your detailed response. I apologize that I was not more clear in my initial post. I'm not intending to keep a blackwater or clearwater tank. This is a 600 gallon display tank - the plan is to keep a normal planted display aquarium that is scaped to mimic a flooded river forest (hence the botanicals in the sand). The intent is to keep fish species from blackwater and clearwater habitats, keeping in line with the flooded river forest theme. Given the size of the tank, the key focus for maintenance is on automation and hence the automatic water changes and dosing pumps. I don't intend to implement any routine that requires my intervention any more than once a month. Everything else I shared was just what I've tried before in this tank system and sharing that using low conductivity alone (i.e. pure RO) without tannins only work for some species if fish and not all. Again, it's my fault for not being clear and I apologize.

That being said, over the past week I've actually gone and did a major rework of the systems in my fish room. I will no longer be using an ro system with a barrel for my auto water changes. Instead, I've purchased 2x 3 stage tap water filters to be set up in place of the barrel, which is now in storage. One of the filter systems will be set up to drip a constant flow 24/7 into the tank at a rate of about 2-3 gallons per hour, which would give me an approximate 10% daily water change. The sump is already drilled with an outlet directly into the drains. Doing this I can change more water in the big tank while still using less water since I no longer have to deal with RO waste water (which has been going directly into the drain). I believe I can even increase to 15% daily water changes this way and still use less water. The other filter system will be used for normal water changes for all the other tanks in the fish room. My tap water tests at 0 kH, 7 gH and about 90 tds so it should still be pretty suitable for soft water fish. The RO system and barrel are in storage close by so if I decide to keep any extreme blackwater fish in the other fish room tanks the system can be set up on a temporary basis for the duration that I maintain those species.

In terms of CO2 and pH, I'm intending to use the pH controller on my Neptune Apex to keep pH levels constant. Yes alot of CO2 will end up being wasted, but CO2 refills are pretty cheap here - it should be <$50 for a 10 litre co2 cylinder refill. I'm using CO2 because I want the plants to grow well - I'm only using hardier plants because of light limitations and maintenance issues arising from the 4ft height of the tank, but even hardy plants grow better with CO2 supplementation. The intent of this tank is ultimately be a display tank that mimics (but not replicates) nature so lush greenery is a bonus (and in line with the flooded river forest theme - wet season not dry season).

I also have a 4 head dosing pump already set up so that will dose fertilizers for the plants and kH solution if needed. I am also considering creating a concentrated blackwater solution by boiling a lot of cattapa leaves and rooibos tea and straining the resulting solution, then dosing it daily to replenish tannins in the water from the daily water changes. It's troublesome but I can manage doing that once a month (with some help from my wife). I've read that such concentrated blackwater solutions can sometimes grow fungus and I've already purchased the food grade preservatives to use for whenever I embark on this project. Research on the feasibility of this blackwater dosing system was actually done several years ago and I think that it would work.
 

illumnae

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5 Year Member
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68
Something interesting I came across that may explain why pure RO didn't work well for many fish for me, but pure RO with tannins works well:

 

MacZ

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Location
Germany
Something interesting I came across that may explain why pure RO didn't work well for many fish for me, but pure RO with tannins works well:

Not the first article on that topic and the reason I advertise RO only in combination with humic substances.

My tap water tests at 0 kH, 7 gH and about 90 tds so it should still be pretty suitable for soft water fish.
Means, if you want to use CO2, you will have to add KH, which will bring you to at least 110, maybe 120 mg/l TDS if you add enough for 2°KH.

I'm only using hardier plants because of light limitations and maintenance issues arising from the 4ft height of the tank, but even hardy plants grow better with CO2 supplementation. The intent of this tank is ultimately be a display tank that mimics (but not replicates) nature so lush greenery is a bonus (and in line with the flooded river forest theme - wet season not dry season).
Limited light is an argument against CO2 in my opinion. I'd consult @dw1305 on this topic. He's the plant expert here on the forum. At least in comparison to me.
And maybe you overestimate the aquatic flora of flooded forests. All I see on footage from there are terrestrial plants and barely any aquatic plants.

I am also considering creating a concentrated blackwater solution by boiling a lot of cattapa leaves and rooibos tea and straining the resulting solution, then dosing it daily to replenish tannins in the water from the daily water changes. It's troublesome but I can manage doing that once a month (with some help from my wife). I've read that such concentrated blackwater solutions can sometimes grow fungus and I've already purchased the food grade preservatives to use for whenever I embark on this project. Research on the feasibility of this blackwater dosing system was actually done several years ago and I think that it would work.
- It would be much more efficient and not susceptible to going bad, if you just add the leaves to the system in an aerated canister.
- Boiling the stuff basically destroys many if not most of the compounds you want in the water.
- Preservatives, food grade or not, are to me a clear no-go.

Good luck then. :)
 

dw1305

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Wiltshire UK
Hi all,
Means, if you want to use CO2, you will have to add KH, which will bring you to at least 110, maybe 120 mg/l TDS if you add enough for 2°KH.
I don't really see any advantage to CO2, it only aids plant growth if none of the other mineral nutrients are limiting. The pH changes due to CO2 addition are a pretty strange and I don't think there is any advantage for pH control either.
Limited light is an argument against CO2 in my opinion. I'd consult @dw1305 on this topic. He's the plant expert here on the forum. At least in comparison to me.
And maybe you overestimate the aquatic flora of flooded forests. All I see on footage from there are terrestrial plants and barely any aquatic plants.
I'd look on all the trees in the flooded forest as aquatic (rather than strictly terrestrial) plants, just large emergent ones.

This is from @Tom C <"Collecting in the Río Tapiche drainage"> page.

resizeimage-aspx-image-2995-jpg.182068

I am also considering creating a concentrated blackwater solution by boiling a lot of cattapa leaves and rooibos tea and straining the resulting solution, then dosing it daily to replenish tannins in the water from the daily water changes.
Have a look at <"https://www.seriouslyfish.com/all-the-leaves-are-brown/">.

<"I'd definitely have a floating plant">, and I believe you can find Water Lettuce (Pistia stratiotes) pretty widely in the Peruvian Amazon basin, there is a picture in <"https://www.tomc.no/page.aspx?PageId=64">.

cheers Darrel
 

anewbie

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1,374
This thread is confusing me because i am using pure ro water in my discus aquarium without leaves and similar. It does have drift wood and live plants - i've not noticed any deaths among my cardinals (2+ months); wc blue rams (3 1/2 weeks); discus (5 weeks - first in qt tank and now the 180 both with pure ro water).
-
I'm trying to decide if i should be panicky and if i need to immediately add something to the aquarium or my fishes are going to die or this isn't relevant to my stocking.
 

illumnae

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5 Year Member
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68
Thank you both Macz and Darrel for your further advice. I've come across Darrel's posts many times over the years at the plantedtank forum, where I've been a member since 2007 and have kept many successful high tech and low tech planted tanks since then.

I'll be running non-limiting nutrients in the tank both via long term root supplementation in the substrate and daily water column dosing. When I refer to light limitations I'm actually referring to the fact that consumer grade planted tank lights are not engineered to penetrate 4ft height tanks and so at substrate level, the PAR would be lower than in a typical high tech planted tank. Actual lighting for the tank is not low (the plan is for 2-3 units of Chihiros Vivid II 10th Anniversary Edition lights, which is a lot of light). CO2 supplementation is essential in these circumstances not just for plant growth, but also for algae prevention.

I've done a test over the past month on one of the smaller tanks in my fish room (40 gallons) and despite my tap water testing at 0 kH, I've experienced no pH crashes or instability despite running CO2 at about 4 bubbles per second in a high tech planted set up (using a Chihiros RGB Slim). I think perhaps the test kit shows 0, but actual kH is between 0 and 1 so it's present, just very low. CO2 supplementation doesn't actually affect kH anyway.

Using a pH controller rather than a timer to control CO2 supplementation is just something I was thinking off to avoid pH swings in the tank since I have the hardware for it set up on my tank regardless. I did read before that pH changes in an aquarium caused by CO2 supplementation are not "real" and don't actually affect the fish - not sure how true this is though. I can equally easily just use a timer to turn the CO2 solenoid on and off.

One last question that I have - if I use a canister with an air stone to soak the cattapa leaves before dosing the liquid into the tank, how many days would you say it would be before the leaves are deemed "exhausted" and can be removed from the canister? I want to avoid the leaves breaking down completely in the canister and the dosing pump dosing sediment and getting clogged.

Thank you again!
 

MacZ

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Germany
Can't say much to the CO2, because it's simply not my field.

Concerning the leaves: Leave them in for a week, then just move them to the tanks. They will release the good stuff until they are broken down to mulm.
 

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