Pygmy Corys in Hard Water?

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JackGulley

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I have a 20 long with platys, zebra danios, WCMMs, and cherry shrimp. I recently rescaped it and wanted some bottom feeders to grace its terrain, so I ordered 6 pygmy corys at the LFS which will be here to pick up on Wednesday.

But, I just read that most corys, including pygmies, prefer soft water, and I've been keeping my water pretty hard* for the livebearers and shrimp. How serious is the soft water thing? I'm not sure what to do.

*abt 150 GH, 120 KH, pH 7.2. My tap water is soft but I use crushed coral in the filter because I've had problems with failed shrimp molts.
 
Hi!
There are some corydoras species that can live in harder water - off the top of my head since I have hard water and had help researching, bronze corydoras and sterbai cories can tolerate quite hard water, I keep both, and a group of six of either of those species (one or the other, or six of each, but that would be overstocking in a 20L. But a group of six of either of those would work, and there are a few more that can manage harder water too, but I can't remember those right now I'm afraid. Most, like pygmies, do need soft water, and are likely to have shorter lifespans and less likely to breed if the water is too hard for them, since the excess minerals they retain cause internal blockages, like blocking the kidneys.

So yes, the soft or hard water issue is important, as you've already discovered with the shrimp moulting issue, and you researched and worked to correct it, which is awesome!

Having said that, I don't think your water is that hard, in the fishkeeping sense, and might work for pygmies! I'm not sure, need @Essjay or someone else who is smarter than I am like @Seisage or @GaryE to do the conversion for the GH for us, if you guys don't mind! :D ♥️

Seriously Fish is a reliable and accurate website that has profiles for most every fish you'll come across in the hobby, and is really useful for checking things like the GH range, temp range, pH range, and their general habitat, preferences, tank sizes, and compatibility.

For pygmy cories, Seriously Fish gives this range:
Temperature: 72 to 79°F (22 to 26°C)

pH: 6.4 to 7.4

Hardness: 2 to 15°H but preferably below 8.

Here's the link to the SF profile if you want to dive deeper! I don't know how to convert the H to GH, but I think that your 150 GH might be within that range. Not totally sure on that though, so if you can work out the conversion, or wait for one of the people I tagged to figure it out, then it might be fine. :)

Pygmy corydoras are wonderful little fish, so it's a good choice, and a 20g long with that larger footprint is great, you can do a lot with a tank that size and shape. I wish they were more available in the UK!

My tapwater is pretty hard, at 253 GH, so my larger tanks have hard water tolerant fish like mollies and the above mentioned bronzes and sterbai, but I have a smaller tank with a breeding colony of pygmy cories, and some otocinclus which I keep softer. I can't afford/deal with the hassle of RO, but I fortunately have water barrels that collects rainwater, and I do a 50/50 mix of my tapwater and the rainwater so the GH is lower in that tank for those soft water fish, and add botanicals like oak leaves and alder cones to add tannins and lower it further. It's my compromise, since yes, the vast majority of fish in the hobby evolved to live in soft water.

But you're fortunate to have softer tapwater, gives you a much wider range of options! If the current tanks harder water turns out to be too hard for pygmies, it's the perfect excuse to set up another tank. That's how we wind up with MTS - Multiple Tank Syndrome - a serious and common syndrome in this hobby! :lol:

But platies certainly need hard water, and tend to fail to thrive if the water is too soft for them. Worth looking up all the species you have, and any you want to add, on Seriously Fish. Make a note of their hardness and temp range etc, and compare, to make sure their ranges all work with the hardness of your water. Gives you a much better chance at long term success. But it sounds as though you're doing well and making thoughtful choices, and wanting the best for the fish, and that's the most important thing.

Would love to see the tank if you feel happy to share a photo, and welcome to the forum! :hi:
 
Adora's pretty on the money with her explanation. As she mentioned, there are some corys that can tolerate harder water. To be honest, most of the popular or well-known fish in the aquarium trade are relatively adaptable. However, I will always drive this point home: there's only so far that you can push evolution. Corys are fundamentally softwater fish. Their genus is endemic to South America. While some can adapt to harder water, they will indeed have shorter lifespans than normal due to calcium buildup in their kidneys, which are not designed to process high concentrations of dissolved minerals. To be honest, a fairly high proportion of popular fish in the trade are softwater fish... It makes me very grateful to have naturally very soft tapwater haha. So, if your tapwater is also soft, it may be worth it, moving forward, to just focus on species that fit your natural parameters, that way you don't have to fuss as much with altering water chemistry.

The parameters you gave are actually just out of the recommended range for pygmies. Even though the range is up to 15 dGH according to SeriouslyFish, the preferred upper limit of 8deg converts to about 140ppm GH. Your corys will probably be okay, although there's a good chance they'll live shorter than expected. You might also want to check with your LFS about their water parameters. If they're very different from your tank, you might need to drip acclimate them to your water.

Here's a fantastic website for converting degrees to ppm and vice versa! There are other calculators around online too, but this one's nice and straightforward

Edit: Oh, and I can definitely second Adora's recommendation of the SeriouslyFish website. It's a fantastic database of fish and their husbandry needs. They don't have some of the more obscure species, but their information for the species they do have is absolutely fantastic. They've become a very respected website for care requirements.
 
To be honest, a fairly high proportion of popular fish in the trade are softwater fish... It makes me very grateful to have naturally very soft tapwater haha. So, if your tapwater is also soft, it may be worth it, moving forward, to just focus on species that fit your natural parameters, that way you don't have to fuss as much with altering water chemistry.

When I joined the forum and learned about the hard water/soft water thing, I was gutted, since I had some otocinclus and had fallen in love with otos, and discovered my water is pretty hard.

The options for people with hard water are pretty much livebearers, cichlids, or rainbowfish. Not personally drawn to cichlids, or balancing their aggression, and while a large rainbowfish tank is stunning, I didn't have space for a large enough tank, the cash for the larger rainbowfish species, and I don't love the shape they tend to get as they age. Kept livebearers, and love my mollies and some guppies and endlers, but constantly monitoring their breeding and overstocking, and finding homes for them or shops that will accept the young is such a hassle, and got wearing after a few years.

But, I'm doing what I can to enjoy my otos and pygmies since I can soften a smaller tank, and working with what I have... the psuedomugli are a lovely option for a more nano sized rainbowfish.

But I'm so jealous of you folks who have soft water straight from the tap! The whole world of fishkeeping is open to you :p I have and would seriously consider moving house, specifically to an area with soft water. I'm that serious!
 
When I joined the forum and learned about the hard water/soft water thing, I was gutted, since I had some otocinclus and had fallen in love with otos, and discovered my water is pretty hard.

The options for people with hard water are pretty much livebearers, cichlids, or rainbowfish. Not personally drawn to cichlids, or balancing their aggression, and while a large rainbowfish tank is stunning, I didn't have space for a large enough tank, the cash for the larger rainbowfish species, and I don't love the shape they tend to get as they age. Kept livebearers, and love my mollies and some guppies and endlers, but constantly monitoring their breeding and overstocking, and finding homes for them or shops that will accept the young is such a hassle, and got wearing after a few years.

But, I'm doing what I can to enjoy my otos and pygmies since I can soften a smaller tank, and working with what I have... the psuedomugli are a lovely option for a more nano sized rainbowfish.

But I'm so jealous of you folks who have soft water straight from the tap! The whole world of fishkeeping is open to you :p I have and would seriously consider moving house, specifically to an area with soft water. I'm that serious!
I imagine you're probably in southern England? I hear the water there is basically liquid rock! Definitely seems like a pain to deal with. I'm glad you at least have plenty of rain at your disposal 😁

Honestly, I'm lucky I've never been interested in any of the livebearers. That way, I don't feel like I'm missing out with my super soft water. And, really, I do mean super soft. My tap water is about 2deg (35ppm) for both GH and KH, although we're in our rainy season right now, so I expect it to go up a bit during our dry summers. I'll be honest, the low KH has made cycling a challenge. I'm glad I adopted an existing tank that's already mature, so I can just seed a sponge filter in there because I wouldn't be able grow a typical nitrobacter-based colony with such low KH. It's also meant that the pH in my new tank has slowly been creeping down with so little carbonate buffer. It's sitting at a 6.6 now! In some ways, that's alright since I plan on keeping blackwater fish, but still... I may not ever have a proper nitrifying bacteria colony, but there's basically no free ammonia at that pH anyway, and I have lots of floating plants that will happily eat up all the ammonium.

Anyway, to bring it back to the thread topic... yes, it is tough to have to work around native water parameters, and hard water fish options in the hobby are sadly fairly limited. If it were me, I would honestly just set up a new tank for the corys and any other softwater fish you want to keep, using your native tapwater. If you want more fish for your harder water tank, pseudomugil rainbowfish would be fantastic. They're such beautiful little fish. If you specifically want bottom dwellers, you miiiiiight be able to get away with some of the smaller synodontis catfish, which are definitely hardwater fish. Just check their requirements on SeriouslyFish. Otherwise, more shrimp or nerite snails are always a good choice.
 
Oh, I forgot I also wanted to mention this. It's possible you might actually not need to keep your water that hard for your shrimp. I haven't tried it myself, so take this with a grain of salt, but I've heard if your water isn't hard enough for proper molting, you can feed your shrimp food that's supplemented with calcium and other minerals. I think most commercial shrimp-specific foods are supplemented. Maybe you've already tried this, but I figured I'd at least suggest it in case you haven't!
 
Great advice in here already but just to chip in some hardwater alternatives to Pygmy Cories have a look at Rosy Loaches, they come from mountain streams that fluctuate in hardness through the year and are pretty robust. A lot of the streams they are found in are limestone beds so in dry seasons get quite hard and they are seemingly closely related and cross over with a lot of Lake Inle species - Lake Inle is a very hard water habitat but also quite heavily populated by what we call nano species.

I have a group of 12 in one of my tanks and they are doing great - I've kept a different group a few years ago too and they did great.

Wills
 
That hardness is fine for cherry shrimps. I have these shrimps and my water is slightly softer.

Neocaridina are so hardy and adaptable aren't they! Love that about them.

Is it a bit too hard for pygmy cories though?

The advice about looking up fish on Seriously Fish and generally in future trying to choose fish that suit your water parameters is spot on. It just makes things a lot easier, rather than trying to change and adjust your tank(s) waters parameters all the time. Although I still struggle with that myself! Rosey loaches are a wonderful suggestion, they're so cute and active!
 
Thanks for all the advice! I think I will go ahead and pick up those pygmy cories, but I will try to alter hardness to be a little bit softer. Those rosy loaches look very tempting tho! Especially because they look like a cross between cories and otos, which I would also really like to get. If I wasn't so close to getting the cories I'd probably try to find them. Are they common to find at aquarium stores? I've never heard of them before.
 
Oh, I forgot I also wanted to mention this. It's possible you might actually not need to keep your water that hard for your shrimp. I haven't tried it myself, so take this with a grain of salt, but I've heard if your water isn't hard enough for proper molting, you can feed your shrimp food that's supplemented with calcium and other minerals. I think most commercial shrimp-specific foods are supplemented. Maybe you've already tried this, but I figured I'd at least suggest it in case you haven't!
I actually use that type of food, but what I've found is that it seems to be intended for an all-shrimp tank, and that in a community tank with not-a-ton of shrimp the fish are very likely to find it before the shrimp do. Between concern for the shrimp and noticing how much more excited the platies were to find this stuff on the ground than to eat the flakes at the surface, I've decided to switch to repashy gel food instead, because I can put a chunk of it on the bottom for all the denizens to find.
 
Water hardness follows the following guidelines. The unit dH means``degree hardness'', while ppm means ``parts per million'', which is roughly equivalent to mg/L in water. 1 unit dH equals 17.8 ppm CaCO3. Most test kits give the hardness in units of CaCO3; this means the hardness is equivalent to that much CaCO3 in water but does not meanit actually came from CaCO3.

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
from https://fins.actwin.com/aquariafaq.html
 
I actually use that type of food, but what I've found is that it seems to be intended for an all-shrimp tank, and that in a community tank with not-a-ton of shrimp the fish are very likely to find it before the shrimp do. Between concern for the shrimp and noticing how much more excited the platies were to find this stuff on the ground than to eat the flakes at the surface, I've decided to switch to repashy gel food instead, because I can put a chunk of it on the bottom for all the denizens to find.
Yeah, that makes sense. If you're motivated to problem-solve, you could try to find a structure that the shrimp can get into but the platies can't. Could be manmade or a piece of wood or rock, as long as it has an entrance the shrimp can fit through but the fish can't. Potentially a small terracotta plant pot? If you put the food on the substrate, then place the pot upside-down over the food, the shrimp could get in through the little drainage hole. Then, you could just remove the pot after some time, once the shrimp have had a chance to eat.

But, anyway, even so, the platies still need the hard water as well. So, my recommendation would still be to put the corys in that tank for now, but set up another tank that uses your soft tapwater and move them into that one.

Will otos work at this hardness?
No, otos are also endemic to South America and are also softwater fish. In fact, they have even lower tolerance for hardness than corys do. Plus, it can be difficult to source ones that aren't starved and they can be difficult to feed once you do have them. It's recommended to have a very mature tank that has a lot of available biofilm in general (not just algae. They won't eat things like hair algae). Even if the hardness wasn't an issue for them, they could very easily be outcompeted for food by the shrimp and potentially by the corys as well

Adding to reiterate: you should really look through the SeriouslyFish website. They have a lot of this type of information about basic water parameter requirements available for a lot of species.
 

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