Safe Rate to Adjust General Hardness

PearlGourami28

Member
Hello!
I have a problem keeping tetras - I posted earlier about how 6 cardinals died in my care. After that, I went for neons, thinking they were hardier/easier to keep and cheaper in case of another disaster. Well, I had 15 and now I'm down to 7. I think it's due to the general hardness of my tank, because the rest of my parameters are good (0 ammonia, 0 nitrite, 10 nitrate, pH 8.0, temp 76). My LFS tested my water for me and confirmed these values.
I used the Sera gH test kit to test my hardness and it's at 20 dgH (yikes). I found and online converter and I think this is roughly 350 ppm total dissolved solids. I want to get this down so that I can keep tetras (my guppies, danios, SAE, and corydoras are doing well with the current conditions).
My question is, how quickly should I decrease gH? I know it's done by adding RO water at water changes. Can it be done all at once? Like a 50% water change out and replaced with RO? Should it be done more gradually, and if so, at what rate? Over days, weeks, months? I don't want to make a bad situation worse by changing parameters too quickly, but I also don't want the remaining tetras to die.
 

Heron

Member
If your GH is that high its probably best to reduce it reasonably quickly. According to a book I have you can decrease the GH about 2 units a day and can increase it much quicker. The change may cause a degree of stress to the fish but keeping tetras in very hard water will stress them just as much so its possibly better to get it down over a few days. If it were me I would change about 25% of the water each day until it drops to a GH of no more than 6.
Be aware RO water also contains no KH so this will also drop with the dilutions , if the KH gets too low your pH could become unstable. If you have a KH test I would keep an eye on it. If it gets low you can raise it with either a KH up product or with some sodium bicarbonate from the supermarket.
 
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PearlGourami28

Member
Heron said:
If your GH is that high its probably best to reduce it reasonably quickly. According to a book I have you can decrease the GH about 2 units a day and can increase it much quicker. The change may cause a degree of stress to the fish but keeping tetras in very hard water will stress them just as much so its possibly better to get it down over a few days. If it were me I would change about 25% of the water each day until it drops to a GH of no more than 6.
Be aware RO water also contains no KH so this will also drop with the dilutions , if the KH gets too low your pH could become unstable. If you have a KH test I would keep an eye on it. If it gets low you can raise it with either a KH up product or with some sodium bicarbonate from the supermarket.
Great, thank you for your reply! I will start with a 25% WC today and test to see where it's at. I will also get a KH test. What are good parameters for KH?
 

Heron

Member
PearlGourami28 said:
Great, thank you for your reply! I will start with a 25% WC today and test to see where it's at. I will also get a KH test. What are good parameters for KH?
A KH of 3-4 should be enough to keep the pH stable but a higher KH won't do any harm
 

MacZ

Member
First of all I would for sure measure the KH, before doing anything, so I know to what percentage to dilute safely.

If it wasn't for the guppies you could very well go down with KH to almost zero all the other fish would not mind that and a low pH as well.

3-4°KH are definitely ok to keep the pH high enough for the livebearers.

Just a sidenote: TDS measures everything, not only hardness, including nitrates and other organic matter that's solved in the water.
Also cardinals and neons are far from the most robust tetras there are. Cardinals are a hit or miss. Either super healthy or they die one by one within a week. Neon tetras are generally not the healthiest fish and need a lot of attention at first. Those that make it past a certain point become virtually indestructable.
In any case I don't think it's the GH alone, the pH of 8 is really hard on those fish, though they can be acclimated to higher numbers.

Just for comparison: I keep cardinals in a bit less than 3°GH, 0°KH and 6.0 pH, the GH and pH are still higher than what they would encounter in the wild. That would be no option with the Guppies of course.
 
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PearlGourami28

Member
MacZ said:
First of all I would for sure measure the KH, before doing anything, so I know to what percentage to dilute safely.

If it wasn't for the guppies you could very well go down with KH to almost zero all the other fish would not mind that and a low pH as well.

3-4°KH are definitely ok to keep the pH high enough for the livebearers.

Just a sidenote: TDS measures everything, not only hardness, including nitrates and other organic matter that's solved in the water.
Also cardinals and neons are far from the most robust tetras there are. Cardinals are a hit or miss. Either super healthy or they die one by one within a week. Neon tetras are generally not the healthiest fish and need a lot of attention at first. Those that make it past a certain point become virtually indestructable.
In any case I don't think it's the GH alone, the pH of 8 is really hard on those fish, though they can be acclimated to higher numbers. I keep cardinals in a bit less than 3°GH, 0°KH and 6.0 pH, the GH and pH are still higher than what they would encounter in the wild.
Good to know - I suppose I was under the assumption that the neons were fairly hardy given that they're sold everywhere - but it's probably that they breed thousands of them and only a small amount survive. Hopefully the 7 left are indestructible.
What are some more generally healthy, small/nano fish that would do well in my current set up? I'm looking to add some color. The majority of these fish are very bland black/white/silver - even the guppies. I have 4 female mutt guppies that are not striking at all, and 1 male blue guppy - he's the prettiest one in there right now.
I see by your signature you're not very fond of community aquariums to begin with so maybe you're not the best person to ask
It's a 36 gallon bow front with sand substrate and tons and tons of plants, if that helps your recommendation for tetras.
 

MacZ

Member
I was actually going to say I might not be the best person to ask. Just removing the guppies would make your stocking a really nice softwater community, which is something I can work with, as the water parameters don't diverge massively and the fish can be kept together without any issues. Often biotopes in South America, Africa and South East Asia have similar conditions. It's very often the livebearers that make the whole thing too complicated and prone to instabilities and mistakes.

Anyhow: Ember tetras if it's really a sea of green. Those are usually hardier than most tetras and probably pretty much what you are looking for.

And post a picture of the tank, please.
 
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PearlGourami28

Member
MacZ said:
I was actually going to say I might not be the best person to ask. Just removing the guppies would make your stocking a really nice softwater community, which is something I can work with, as the water parameters don't diverge massively and the fish can be kept together without any issues. Often biotopes in South America, Africa and South East Asia have similar conditions. It's very often the livebearers that make the whole thing too complicated and prone to instabilities and mistakes.

Anyhow: Ember tetras if it's really a sea of green. Those are usually hardier than most tetras and probably pretty much what you are looking for.

And post a picture of the tank, please.
Ember tetras are super pretty, I will definitely consider them. As requested, here's a picture of my current set up. I needs some TLC - I will prune some stuff down this weekend.
 
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PearlGourami28

Member
Okay everyone, here's an update. I have my general hardness down to 10 degrees general hardness, and my kH at 6 degrees carbonate hardness. My pH is reading at 7.6 on the normal API test and 7.4 on the high range pH test. Ammonia 0 Nitrite 0 Nitrate 5. Is this stable/healthy for the inhabitants?
Would adding crushed coral be a good idea to prevent against any sudden fluctuations in pH if I continue to do water changes with R/O water?
 

Corylover123

Member
The hardness isn’t your problem probably it’s most likely the ph
get rodi and remineralize it
 
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PearlGourami28

Member
Corylover123 said:
The hardness isn’t your problem probably it’s most likely the ph
get rodi and remineralize it
how do you remineralize it?
 

Corylover123

Member
Baking soda and other commercial products I don’t know exactly because I don’t care about water hardness because my ph is 7 and stable I have the same hardness as you and it’s fine you need rodi I would do a 70% ro 30% desert water (arizona has desert water and it’s disgustingly hard) you are gonna kill most tetrss
 
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PearlGourami28

Member
Corylover123 said:
Baking soda and other commercial products I don’t know exactly because I don’t care about water hardness because my ph is 7 and stable I have the same hardness as you and it’s fine
okay so you suggest I put in peat moss or indian almond leaves to reduce my pH but keep the hardness the same?
 

Corylover123

Member
No it won’t change , your water hardness makes it more stable and the ph is harder to change
 

Pfrozen

Member
PearlGourami28 said:
Okay everyone, here's an update. I have my general hardness down to 10 degrees general hardness, and my kH at 6 degrees carbonate hardness. My pH is reading at 7.6 on the normal API test and 7.4 on the high range pH test. Ammonia 0 Nitrite 0 Nitrate 5. Is this stable/healthy for the inhabitants?
Would adding crushed coral be a good idea to prevent against any sudden fluctuations in pH if I continue to do water changes with R/O water?
There's nothing wrong with a pH of 7.4-7.6

Your fish should be fine with that KH and GH

imo you already changed it, you don't need to change it again unless you experience problems
 
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PearlGourami28

Member
Corylover123 said:
Baking soda and other commercial products I don’t know exactly because I don’t care about water hardness because my ph is 7 and stable I have the same hardness as you and it’s fine you need rodi I would do a 70% ro 30% desert water (arizona has desert water and it’s disgustingly hard) you are gonna kill most tetrss
okay good to know thank you, yes I'm in arizona with incredibly hard and alkaline water.
 

MacZ

Member
PearlGourami28 said:
Okay everyone, here's an update. I have my general hardness down to 10 degrees general hardness, and my kH at 6 degrees carbonate hardness. My pH is reading at 7.6 on the normal API test and 7.4 on the high range pH test. Ammonia 0 Nitrite 0 Nitrate 5. Is this stable/healthy for the inhabitants?
Would adding crushed coral be a good idea to prevent against any sudden fluctuations in pH if I continue to do water changes with R/O water?
Your readings are absolutely fine now, there is no need to do anything else.
"sudden fluctuations in pH" are not going to be expected with that KH-reading. And even with a KH of zero massive mistakes in maintenance would be necessary to get fluctuations.

But remember to stick to the mixing ratio of RO to tap you have reached now.

And about the IALs: Botanicals of any kind do not have significant impact on pH unless KH is below 1-2°.
 
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PearlGourami28

Member
MacZ Thank you for all your help!
 

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