Raising soft water fish in hard water: do i need to use ro water?

[seaMate]

I was thinking…
If my LFS fish have been bred in hard water, does that mean I can get away with not using RO water?

[bettaMagenta]

I've got some thoughts on this. Most local fish stores, from what I've seen, can't breed fish fast enough to keep up with demand, so they often get shipments in to supplement their stock. This means the fish you're getting might not be bred in-house, even if the store does have a breeding program.

Personally, I've got hard, alkaline water at home, and I've had a tough time keeping soft-water fish. I've had some success with Asian fish and plecos, but most of my soft-water fish just didn't make it. That was until I installed a dedicated RO unit for my aquariums. It made a big difference. I've also had good luck with rainbow fish and other species that can tolerate hard water, even if they don't naturally prefer it.

[Burgermuncher]

I've found that keeping fish outside their normal water hardness can be done, but they rarely thrive and some won't even survive. @bettaMagenta's point about store-bred fish is well-taken - they're usually not in the store long enough for it to make a difference. Sticking to fish that match your local water conditions tends to minimize issues. Using RO water or mixing water can be a hassle to maintain, and often isn't worth the trouble.

[WildFins]

Honestly, it's pretty simple - you've got great options either way, whether you're dealing with soft or hard water. Working with what you've got is usually the way to go, rather than trying to force a specific parameter.

[graye]

There's a significant distinction between the water parameters fish can survive in and those required for successful egg development. It's likely that softwater fish from rainforest habitats are bred in Asian fish farms with similar water conditions, before being shipped to your local store.

My experience with breeding softwater species in medium-hard water has shown that fry production is significantly lower. Fish farms, driven by demand for South American species, often opt for locations with softer water to maximize their yield.

Many hobbyists successfully keep fish outside their natural water parameters, but I've found that matching the fish to the water can greatly impact their lifespan. I recall being thrilled when my cardinals lived up to five years in my 140ppm water, but after switching to 80ppm tapwater, they began living up to seven to nine years and beyond. While this is just one anecdote, there's credible evidence suggesting that softwater fish may have shorter lifespans in harder water.

However, it's also worth noting that cardinals are reportedly seen as annual fish in the wild, with a one-year lifespan. This raises questions about the relationship between lifespan and quality of life – a topic I don't have a clear answer to.

[angelica]

I used to keep soft water fish in hard water, thinking it wouldn't be an issue. But in hindsight, I can see the impact it had on their lifespan - my cardinals and other soft water fish averaged 12-18 months. Since switching to RO water, I've noticed a significant difference. The same species are now thriving, with an average lifespan of 6-7 years. The change has also had a profound effect on their appearance, with much brighter colours now on display.

[WildFins]

Evolution has a massive head start over a few generations of selective breeding.

[belleora]

I've been thinking about this a lot, and from what I've gathered from discussions here (maybe @boomer or @sSjey can dig up the studies), it seems that soft water fish have evolved to hold onto minerals when they can, since they're scarce in their natural environment. On the other hand, hardwater species like mollies have adapted the opposite way.

The issue with keeping soft water fish in hard water long-term is that the damage is cumulative. Over time, the minerals they retain can cause blockages, particularly in the kidneys, which ultimately leads to a shorter lifespan.

I'd love it if someone could share the research to back this up - I'm sure I've seen papers on this shared here before, but I don't have the time to track them down right now.

[seaMate]

My water's through the roof, 280ppm or so, I'm just gonna stick with livebearers for now and maybe some rainbow fish, they seem to handle the hard water alright. I'll think about getting an RO filter down the line, but for now I'm good. Thanks for the advice, guys.

[belleora]

I was thinking…
If my LFS fish have been bred in hard water, does that mean I can get away with not using RO water?

If you're not ready to invest in an RO filter just yet, there are a couple of alternatives you could consider. I've found that collecting rainwater can be a good option, as long as you have a garden and aren't in a heavily polluted area. You'll just need to set up a waterbutt to collect the rainwater.

Another option is to use a mix of rainwater and tap water in your tank. I've done this in my 15.5g tank, using a 50/50 mix of rainwater and my tap water, which has a hardness of 253ppm. This has worked well for me, especially since I wanted to keep otocinclus and pygmy cories. The pygmies have even started breeding, so it seems to be a good solution for us.

You could also consider buying RO water from your local fish store, which is often cheaper than installing your own RO filter.