Blackwater hardness question

[Chummus]

I've been working on a blackwater tank, but after considering stocking I really want to try some crystal red shrimp along with the chili rasboras I plan on keeping. But to get the hardness of the RO water up to 4 dGH, which I read was at the bottom of their hardness requirements, it gets the water from 45ppm TDS all the way to almost 150 ppm.

I'm aware that this wouldn't really be "true" blackwater anymore but is there any reason why this is a bad idea for the livestock or other ways it affects the ecology of the system? If not I think I'll go for it, but if it ruins the ecology I'll just stick to the fish. Thanks.

 

[ruud]

TDS for caridina ....around 100 is typical

You mention 150, which is:
8.4 dGH based on CaCO3
15 dGH based on CaO
21 dGH based on Ca

So feel free to share your calculations

I don't think it's a bad idea for fish to have somewhat higher GH

Blackwater has very low minerals (like GH), hence very low bacteria concentrations, which reflects a less "hardy" immune system

I keep my chocolate gouramis + chili rasboras in RO water with tiny dosing of minerals for emersed plants; TDS is around 40 ppm after dosing then drops to very low over the course of a week; they seem to approve of this

 

[Chummus]

Thanks for your reply. It turns out I misread the GH test on the water from the tank and it was closer 3dGH rather than 1. (at 49 ppm TDS). I don't know where it came from because coming out of the RO unit it has only 2ppm TDS, but at least it's closer to where I need it. Now a little bit paranoid about misreading the tests but it makes more sense now. Thanks again.

TDS for caridina ....around 100 is typical

You mention 150, which is:
8.4 dGH based on CaCO3
15 dGH based on CaO
21 dGH based on Ca

So feel free to share your calculations

I don't think it's a bad idea for fish to have somewhat higher GH

Blackwater has very low minerals (like GH), hence very low bacteria concentrations, which reflects a less "hardy" immune system

I keep my chocolate gouramis + chili rasboras in RO water with tiny dosing of minerals for emersed plants; TDS is around 40 ppm after dosing then drops to very low over the course of a week; they seem to approve of this

 

[Chummus]

I’m at a bit of a loss here, but I’m hoping this forum can help me again as it has in the past.
I started my first blackwater project a month and a half ago, and let it mature for that time. When I tested it a few days ago, I got 6.6 pH, 3dGH, 0dKH. I just added a bit of Seachem Equilibrium to get the hardness to about 4dGH. When I left it the parameters were 6.6 pH, 4dGH, 0dKH 90ppm TDS.
I haven’t touched it since then, and today when I checked it it was 6.8 pH, 7dGH, 4dKH, and 120ppm TDS. The only thing I did in the meantime was add a piece of cholla wood.
This is really discouraging… I didn’t want to have to wait another few months before stocking. Blackwater has been harder for me than I expected.
What should I do next and what would have caused this?
I tested everything multiple times, API liquid tests.
Thanks in advance.

 

[Cherryshrimp420]

What's in the tank? Seems like there's some rock or sand that's leaching

 

[Chummus]

Only Seachem flourite from the previous setup, wood I collected from a lake, oak leaves, and the cholla wood. I suppose the flourite might leach but it's been in the tank for over a year, from the last use of that aquarium.
I also could've had the colors swapped for the KH test last time. I double checked to make sure I had it right this time. So there is a possibility the KH was always up but that still doesn't explain the hardness and pH.

 

[Cherryshrimp420]

Hmm I would check again in a few days and see if any changes.

Also this is assuming you are using RO water?

 

[TClare]

Might have something to do with the equilibrium you added? I don’t think this is at all necessary for a blackwater tank, the water should be as soft as possible. The botanicals act as a buffer to prevent pH fluctuations without significantly raising the TDS.

 

[Itiwhetu]

These are all approximations, so near enough is good enough. Don't try to get exact parameters otherwise you will be chasing your tail.

 

[Chummus]

Hmm I would check again in a few days and see if any changes.

Also this is assuming you are using RO water?

Yes, I'll see if things continue to change over the next few days. And yes, I am using RO water.

Might have something to do with the equilibrium you added? I don’t think this is at all necessary for a blackwater tank, the water should be as soft as possible. The botanicals act as a buffer to prevent pH fluctuations without significantly raising the TDS.

I also think it might have something to do with the equilibrium because it's the only change I made, but I don't see how it could affect the pH or KH unless I'm missing something. I only added a little bit because I want to stock caridina shrimp.

 

[Cherryshrimp420]

Yes, I'll see if things continue to change over the next few days. And yes, I am using RO water.


I also think it might have something to do with the equilibrium because it's the only change I made, but I don't see how it could affect the pH or KH unless I'm missing something. I only added a little bit because I want to stock caridina shrimp.

Seems likely to be some test kit issue. With 4 dKH you wouldnt be able to have 6.8pH unless injecting co2.

 

[TClare]

Have you got plants, and did you measure pH at the same time of day - mine can go from 6.5 to 6.8 from morning to evening as the plants use up CO2 in the water.

 

[Chummus]

Seems likely to be some test kit issue. With 4 dKH you wouldnt be able to have 6.8pH unless injecting co2.

It's hard to discern between 6.8 and 7 pH. Is a pH of 7 possible with 4dKH? I've repeated all the tests a few times so it'd be a strange test kit issue, especially considering it read as 0dKH a few days ago.

Have you got plants, and did you measure pH at the same time of day - mine can go from 6.5 to 6.8 from morning to evening as the plants use up CO2 in the water.

I do have plants but I haven't tried that. Interesting. I will test the pH a few times tomorrow throughout the day.

TDS is also up to 126ppm. I haven't touched the tank so I don't know what is leeching them.

 

[TClare]

TDS could increase if you are losing water through evaporation. It will also increase if nitrates (etc.) increase, as well as anything that might be leaching into the water. Fluorite is meant to be inert, if nothing else is leaching only the equilibrium must have cause the hardness to increase.

 

[Cherryshrimp420]

It's hard to discern between 6.8 and 7 pH. Is a pH of 7 possible with 4dKH? I've repeated all the tests a few times so it'd be a strange test kit issue, especially considering it read as 0dKH a few days ago.


I do have plants but I haven't tried that. Interesting. I will test the pH a few times tomorrow throughout the day.

TDS is also up to 126ppm. I haven't touched the tank so I don't know what is leeching them.

PH should be above 7 so one of the tests is off. This is assuming no co2 injection

Do you have a pic of the tank?

 

[Chummus]

PH should be above 7 so one of the tests is off. This is assuming no co2 injection

Do you have a pic of the tank?

Maybe the pH is a tad higher than 7, I have a hard time telling the exact color. I'll attach a photo of the tank and the pH test. Also tested KH with test strips and it came out the same. No CO2. I also tested the pH in the middle of the night and in the middle of the day. They came out the same

This is really frustrating. Blackwater is turning from something fascinating to me to an annoyance...
Thank you all for your help so far though, it is much appreciated.

 

[Cherryshrimp420]

Maybe the pH is a tad higher than 7, I have a hard time telling the exact color. I'll attach a photo of the tank and the pH test. Also tested KH with test strips and it came out the same. No CO2. I also tested the pH in the middle of the night and in the middle of the day. They came out the same

This is really frustrating. Blackwater is turning from something fascinating to me to an annoyance...
Thank you all for your help so far though, it is much appreciated.

Ah ok that pH makes more sense. Seems like you have some lime/calcium carbonate leaching in the tank. Could be from some pebbles in there or something in the substrate, not sure...

 

[TClare]

Did you read this article Blackwater: Basics and FAQ - If not you might find it helpful.