Water hardness question

Lcc86

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Hi all

I've recently discovered that my water is harder than my local utility company states it is and I have soft water fish because that's the type of water I thought I had. Basically I did an API gH and kH test and it showed 6 drops kH and 12 gH. I haven't got the conversion chart to hand but have attached the results from my water company's website and know it's not soft.

I'm temporarily using RO water due to some ongoing water works for 3 months by my house, and planned to transition back to tap water once its completed. I'm matching the gH and kH to my tap water as I don't want to shock my fish. My question now is when I transition back to tap water, if I use part RO water without remineralising, will that lower the gH and kH naturally?

I have a single betta and a community tank with lots of cories so all soft water fish as I'd assumed based on the info I had that they were compatible with my water!
 

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The water company info is from 2022. They do say it can be different from the quoted as they use multiple sources.

I always found the GH tester to be difficult to read with soft-ish water as the colours are pale with just a few drops added. Actually, I wonder if it was my eyes. I had cataract surgery in 2018 (right eye) and 2019 (left eye) and colours look different now - yellows were almost none existent, and green and orange have a yellow component, maybe that's why 🤷‍♀️
 
You can dilute out the minerals contributing to the GH with RO or distilled water. Make serial dilutions and measure GH in each dilution. Pick the mixture that gives you the GH your fish need.
 
The water company info is from 2022. They do say it can be different from the quoted as they use multiple sources.

I always found the GH tester to be difficult to read with soft-ish water as the colours are pale with just a few drops added. Actually, I wonder if it was my eyes. I had cataract surgery in 2018 (right eye) and 2019 (left eye) and colours look different now - yellows were almost none existent, and green and orange have a yellow component, maybe that's why 🤷‍♀️
Yeah I couldn't find anything else more up to date! The colours are quite bright with my tests so I'm assuming it's accurate. I think I was just surprised at how much higher it was!
 
You can dilute out the minerals contributing to the GH with RO or distilled water. Make serial dilutions and measure GH in each dilution. Pick the mixture that gives you the GH your fish need.
Thanks. I actually hate RO as I don't have capacity for a machine and only have space for one 25 litre bottle, so I'd much rather do without it but obviously want my fish to have water best suited to them!
 
KH 107ppm
GH 215ppm

use a 50/50 mix of reverse osmosis water with tap water and you will have a GH around 100ppm, which is great for Bettas and Corydoras.
 
KH 107ppm
GH 215ppm

use a 50/50 mix of reverse osmosis water with tap water and you will have a GH around 100ppm, which is great for Bettas and Corydoras.
Thanks Colin, will give that a go!
 
The water report show 164 mg/l (ppm)calcium carbonate. Your test kits measure in degrees. 1 degree is about 17.8mg/l You have hard water. Converting 164 ppm to degrees I get 9 degrees consistent with your test kit.
 
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I really don't understand why people get so overwrought about water hardness. Unless you have really hard water (over 400 ppm) the only time it's an issue is with breeding. I have a community tank with discus, wild caught cardinal tetras, corydoras, and 3 other species of dwarf catfish. I've had the discus and the cardinals for about 3 years, the rest over 2 years, and all are doing just fine. My water is 300 ppm plus, give or take. You're more likely to cause problems relying on RO water than you are to solve any.
 
I really don't understand why people get so overwrought about water hardness. Unless you have really hard water (over 400 ppm) the only time it's an issue is with breeding. I have a community tank with discus, wild caught cardinal tetras, corydoras, and 3 other species of dwarf catfish. I've had the discus and the cardinals for about 3 years, the rest over 2 years, and all are doing just fine. My water is 300 ppm plus, give or take. You're more likely to cause problems relying on RO water than you are to solve any.
They might be doing fine in the short term, but the real issue with water hardness is long-term physiological effects. Softwater fish do not have the physiology for processing out minerals from the water that enters their bodies. The result is that their kidneys get mineral buildup over time, which eventually leads to organ failure. So yes, sure, I don't distrust that your fish are doing fine currently, but don't expect them to live to their normal life expectancy.
 
They might be doing fine in the short term, but the real issue with water hardness is long-term physiological effects. Softwater fish do not have the physiology for processing out minerals from the water that enters their bodies. The result is that their kidneys get mineral buildup over time, which eventually leads to organ failure. So yes, sure, I don't distrust that your fish are doing fine currently, but don't expect them to live to their normal life expectancy.
Yes this is what I want to try and avoid. My fish are all absolutely fine now, but if I'd known my water was much harder than I was led to believe I probably would've chosen different fish that were more suited to that. I want to enjoy my fish for as long as possible and have them be healthy. I'll be slowly working on changing the water chemistry over coming weeks/months. I have access to a local RO water seller so the main faff is just going to get the water each time I need to do a water change.

Lesson learned for future, don't rely solely on utility company reports!
 
They might be doing fine in the short term, but the real issue with water hardness is long-term physiological effects. Softwater fish do not have the physiology for processing out minerals from the water that enters their bodies. The result is that their kidneys get mineral buildup over time, which eventually leads to organ failure. So yes, sure, I don't distrust that your fish are doing fine currently, but don't expect them to live to their normal life expectancy.
Can you please point to any scientific studies that show this? There's only one study that I came across and it only included a few species of fish. One of those species was Betta splendens. Ironically, that study found that Betta splendens fry had a higher survival rate in hard water. As I recall, the control group with the highest survival/weight gain was in water with a hardness exceeding 500 ppm. The only negative effect of hard water that I've ever come across is related to egg development.
 
Can you please point to any scientific studies that show this? There's only one study that I came across and it only included a few species of fish. One of those species was Betta splendens. Ironically, that study found that Betta splendens fry had a higher survival rate in hard water. As I recall, the control group with the highest survival/weight gain was in water with a hardness exceeding 500 ppm. The only negative effect of hard water that I've ever come across is related to egg development.
You have correctly identified a large knowledge gap in science. To be honest, in general it's rather difficult to find research on many species in the hobby (except the very common ones like guppies, bettas, zebrafish, and a few tetras). There's even less research on the long-term effects of much of anything on ornamental fish. The thing is, there's very little reason to research these things. That is, there's almost no incentive. Ornamental fish are not particularly economically valuable compared to commercially farmed fish species and it's generally not monetarily viable to conduct years-long studies on any organism, let alone ornamental fish. There are few to no funding agencies that would fund this kind of research. When you do happen to find ornamental fish research regarding environmental factors, it's usually on shorter-term effects like acute stress or, as you mention, reproduction. Or, it's stuff that can be measured in a short time span, certain physiological processes like ion regulation, respiration, waste excretion, etc.

So, no, admittedly I have not been able to find a study that looks at long-term effects of hard water on soft water fish over the course of years. I will certainly keep looking and will get back to you if I find anything long-term. The vast majority of studies I found regarding water hardness effects on fish have to do with commercially farmed species like trout, salmon, and catfish, particularly in making sure there's enough calcium and other minerals in their diets. That's where the money is, so that's what the research is on. It's worth noting that just because a trend has not been quantified and published in a journal doesn't mean it doesn't exist. I'm all for finding academic sources. They're almost always the best sources of evidence we have. And it is good to question commonly held beliefs, but the fact remains that warnings of long-term effects of hard water on soft water fish have been present in the hobby for quite a while. Many common myths in the hobby are absolutely refuted by science, but until someone does the long-term research on the effects of water hardness, I have to go with what has been identified as a trend, even if anecdotally.

Now, this is pure speculation, but it is possible that soft water fish do benefit from higher dissolved mineral concentrations than what is found in their normal habitats. Soft water fish, especially in the Amazon, are well-adapted to quite acidic water with low amounts of dissolved mineral ions. Of course, they need these minerals/ions for various physiological processes. They also experience loss of ions (Na+, Cl-, K+) when exposed to very acidic conditions, although increased levels of calcium ions didn't affect loss rates, so it's questionable whether it's beneficial in that regard (Adalberto et al. 1998).

My speculation is as follows: it seems that fish in soft water have to "work harder" to get enough ions from the water, even if they're adapted to handle it. Water that's harder than their natural habitat may actually benefit them by relieving that constraint. However, I would expect that it's only beneficial to a point and that beyond that point, increased hardness wouldn't benefit them and could potentially have some detrimental effects.

So, I had a look at the paper you mentioned, because I was interested. I had to search for it myself, but I did find it. I noted some things that I'd like to comment on.

You are correct in pointing out that they found increased growth performance for the bettas with increasing water hardness. However, the researchers don't actually mention the period of time over which they measured growth. As per the methods, "growth performance" was determined by measuring adult fish at their sexual maturation. "Growth performance" appears distinct from measures of larval growth, since they're mentioned separately. In that case, what does "growth performance" actually mean? They bought fish from a local aquarium that were old enough to be sexed, so what does "at sexual maturation" mean in this context? How much time was there between initial and final measurements? The researchers don't say, at least not that I can tell. If "growth performance" was the growth of the fry up until sexual maturation, they needed to make that much more apparent because it is not clear.
Edit: Okay, I did find the length of time. It's 1.5 months. I rescind the clarity criticism.

Edit: double-checked the methods and the results table and yes, larval growth performance is distinct from adult growth performance. For the larvae/fry, they only measured length. For adults, they measured length and weight. So, for the adult growth performance, it's still not clear how much time was between initial and final measurements. Also, betta fry growth performance (very bottom row) was actually LOWER at the two highest hardness values.

Screen Shot 2024-03-07 at 2.01.40 AM.png


Ironically, that study found that Betta splendens fry had a higher survival rate in hard water.
No, they did not. Direct quote from the results: "The percentage larval survival of both species declined gradually with the increasing hardness level, reporting significant declines above 320 ppm (p < 0.0009)"

Additionally, it is mentioned that fish were fed twice a day. It's stated that the feeds were 5% of the fish's body weight, but it's also stated that they were fed ad libitum, which in dietary studies usually means organisms were allowed to eat as much as they liked. So, it's not very clear exactly how much food these fish were getting. If they were fed ad libitum, there would probably be significant growth regardless of water conditions. Even if they weren't fed truly ad libitum, two feedings per day of 5% of their body weight is more than what's needed. University of Florida states that fish only need between 0.1-1.0% of their total body weight in food per day. With this in mind, the fish in this study probably would have grown regardless of water hardness. Edit: I'm pulling back a little on this particular criticism because it's true that the adult growth was still significantly higher at the higher hardness levels, so it doesn't really matter that all the fish grew, it matters how much they grew, and the feedings were constant across treatments.

The control treatment, the lowest hardness level in the study, is 150ppm. That is not soft water. Soft water is generally defined as 50-60ppm or lower. So, really, you can't use this study to compare betta growth performance between hard and soft water because the study only uses hard water at increasing levels of hardness.

Lastly, and most importantly, this study is NOT long-term. You cannot use this study as evidence that soft water fish do well, long-term, in hard water. At most, growth potential was measured from hatching to sexual maturity over 1.5 months, which is nowhere near the full lifespan of the fish.

Link to the paper, for those interested in taking a look themselves: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7678082/

Adalberto et al. 1998 (ion loss in Amazonian fish): https://www.journals.uchicago.edu/doi/10.1086/515893
University of Florida feeding guidelines: https://edis.ifas.ufl.edu/publication/FA096
 
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General Hardness

0 - 4 dH, 0 - 70 ppm : very soft
4 - 8 dH, 70 - 140 ppm : soft
8 - 12 dH, 140 - 210 ppm : medium hard
12 - 18 dH, 210 - 320 ppm : fairly hard
18 - 30 dH, 320 - 530 ppm : hard
higher : liquid rock (Lake Malawi and Los Angeles, CA)
 
I was going to jump in, but the water got deeper than I intended to swim in...

"fish" is a pretty generic term, so, some fish live naturally in areas, that the water chemistry doesn't change much through out the year, & some fish live, where there are immense changes in the water, usually seasonally... I would think we could expect fish that live where the water never changes, to not have evolved, to handle water out of their normal range... & expect fish that experience huge changes in their water, are going to be better equipped to handle a wider range of changes... I've not seen, for example, Betta splendens ( since it was used as an example above ) in the wild, but I thought I'd read their environment goes through extreme changes seasonally, if this is the case, they are likely evolved to deal with a wide range of water... if you used an angel fish ( or discus for example ) they probably still go through quite a bit of difference in their water seasonally, but again, from what I've read, the water probably varies between soft, & very soft waters, so they unlikely evolved to handle long term, hard water...

I know I couldn't personally keep an Angel alive in my area with very hard water, for more than 4 months... changing nothing, but adding an RO unit to add water during water changes ( I did not blend the RO & local water to add to the tank, I just did twice a week 5 gallon water changes ( on a 45 gallon tank )) & it took a month & a half, before I started seeing any change to my water tests... at that point I tried a few angels again... & year and a half later, they are not only still living, but thriving...
 
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