Salt...any need for it regularly

[neutrino]

How to check salinity? Answer is fairly simple. They make various hydrometers, refractometers for SW tanks. Some more accurate than others, like most things a question of how much you want to spend. Link

Many fish are more adaptable to a wider range water conditions than some people think-- within reason. The argument that fish have spent thousands (or millions) of years adapting to specific conditions can be overstated. For starters, it assumes their habitat has been unchanged for those thousands or millions of years and doesn't account for the history of many species that have dealt with geological changes, cycles of changing climate, and seasonal or other natural habitat changes, or the number of cichlids that have colonized and adapted to new habitats. Not saying there aren't some extra sensitive species, there are. It does pay to investigate the range of pH, temp, hardness, etc. for keeping an unfamiliar species, but do that, and get enough answers from people with experience, and for most species you'll find a range of conditions that work just fine.

For most fish you can find a happy medium within a range that's comfortable for them. And, no-- I'm not talking about alive but stressed or ok only for shortened life spans. I've had severums live 15 years, haps and peacocks 12, have an L260 pleco still going strong after 12,13 years, currently have Kapampa fronts going on 12, had discus about 6 years old and still going strong when I sold them due to a major move, had green terrors of 12 or more, you get the idea. This is keeping them all at ph in the mid 7s, medium hardness.

You might find this interesting-- link

 

[Jeff5347]

Funny you mention ph.
I was watching a documentary today, although on saltwater, it was very interesting and eye opening regarding the oceans absorbing the atmosphere co2 which in turn drops the oceans ph. Its effects are shell animals and corals unable to make correct shells and corals leading to dying reefs. Very interesting and disturbing documentary

 

[neutrino]

Haven't watched that yet but have seen similar articles, etc. Sad, really, but affecting some species and others not so much. Some species of marine life, including corals, can adapt better than others. Some crustaceans, like lobsters, crabs, shrimps, adapt and build stronger shells while oysters aren't doing as well. The other parts of the equation are pollution and warming.

To get have the whole picture, though, we should understand even ocean habitats see natural pH fluctuations, some more than others, tidal areas, sea vent habitats, etc. As it's been observed, in effect we're conducting a global science experiment and only time will tell how far it goes and what the results will be.

Reminds me to add to my comment above that some species that can be healthy and long lived in a wider range of conditions than their wild habitat suggests might need more specific conditions for successful breeding, viable eggs, etc.

 

[neutrino]

Separate post for separate subject-- returning closer to the original discussion...

If you wanted to target wild habitat conditions, or close, you won't do it by splitting fish into new world vs. old world or SA vs. CA. You'd have to research the specific location, or range, of the species, or closely related species, in question. Very few people do this, most go by common and simplistic assumptions, e.g. discus are soft water, warm water fish, etc. In fact, (wild) green discus and heckle discus are soft water fish, blue/brown discus not as much. Blue/brown discus are very adaptable in their range, seeing pH from 6-7.8 --per Heiko Bleher who has spent many years studying their habitat. And here's one a lot of people don't mention, discus like shade, not the bright lights many keep them with.

SA has 3 types of rivers, white water , black water, clear water, with generally different characteristics. Within each type individual rivers vary in conditions and not just the river system, like Tapajos, but tributaries or bodies in the same region vary. Water in the same location, conductivity, mineral content also varies seasonally, high and low water. Then there's the lakes, a whole other thing, and these vary also.

So, where do your fish come from? Black water, clear water, white water, lake, cenote, coastal, inland, elevation, latitude, cool water, warm water? But wait, within each water type or region or system individual locations can vary. Example: Tapajos-- surveyed as pH 6.56, Tefe-- surveyed as pH 5.06, Jurua-- surveyed as pH 7.27 (link). How widely or narrowly, either geographically or in terms of habitat, is your fish distributed? Here's another thing few people consider, is a particular wild location/habitat already near the limits of its range and/or adaptability for a species that is actually more 'comfortable' in more moderate conditions? And, yes, this happens. So, as I say, the need to match a wild habitat can be overstated.

More power to you if you want to research and faithfully replicate the biotope or conditions of a specific population from a specific location. I respect that approach, though technically this should include seasonal cycles, with their changes in water levels, water chemistry, terrestrial runoff, temperature, available food, etc. But very few fish actually require such a level of precision. Fortunately for us, most fish are reasonably adaptable, more so than some realize. Again, not saying you shouldn't look into an appropriate range of conditions for an unfamiliar fish, but most do well in a moderate range of water conditions, assuming clean water, sufficient space, sufficient oxygen, appropriate temperature range, decent food, etc.