I have seen this many times,
”I put my severum, or oscar in my high pH, hard water when young, and it’s been fine, 3 months, or even a year later.”
But often, maybe 3 years or less later, a post comes up.
“My oscar, or severum has lots of HLLE scars, and I haven’t done anything different.”
There are a couple things to take into consideration, along with the hard water..
One is water change schedule, and because it may be the same now, as it was 3 years ago, that cute little 3” oscar is quadruple that size, and putting out quadruple the waste, but those 50% water changes might be still only once per week.
Results the fish is swimming in fish pee, and fish poop soup, and high nitrates (no matter how great the filtration).
When most people get their tap water, it is 99.999% pathogen free, and close to nitrate free.
As soon as it is dechlorinated, it becomes a great home for nasty bacteria, and the more your oscar pees and poops in the water, the better place it is, for those bacteria to grow, so even with a 50% water change there are 6 days for bacteria to double, triple or more. Many pathogens reproduce at alarming rates.
And here is where the hard water comes into play.
Species that live in soft, tannin filled waters, have evolved (on a cellular level) to live with different bacteria and protozoa, than live in hard water, and evolved to resist those soft water species of bacteria. And tannins themselves are anti bacteria in many cases.
When a soft water fish species, is put in hard water the osmotic pressure, allows hard water bacteria to invade on a cellular level, and cause chronic disease.
I have also heard it said ….
“But my friend raised thousands of discus in hard water”.
Many discus breeders change large amounts of water on a daily basis, sometimes up to 90%, per day, to get good growth.
This is where the 99.9999% pathogen free tap water comes into play.
When those massive water changes are done, beside removing growth inhibiting hormones, and nitrate, they also remove a good portion of those bacteria every day, or even every other day, so bacteria that cause diseases like Hold in the Head are removed, and can’t get a foothold.
Most average aquarists don’t change 90% of the water in there oscar tank, once every week, much less every day.
To give an example of how osmotic pressure works.
When I treat a tank for ick, I add enough salt to bring the salinity (osmotic pressure) to 3ppt. That extra osmotic pressure is lethal to simple celled animals and lyses them.
Most fish are not acutely effected, or killed by that extra osmotic pressure, but it does put chronic low level stress on them, and allows (what would be) normally benign bacteria to enter soft water fish on a cellular level, causing chronic disease like HLLE.
Add an out of the norm osmotic pressure, to high nitrate, and the other stress factors of aquariums like cramped quarters or inappropriate tank mates, and it’s amazing we don’t see even more disease.
”I put my severum, or oscar in my high pH, hard water when young, and it’s been fine, 3 months, or even a year later.”
But often, maybe 3 years or less later, a post comes up.
“My oscar, or severum has lots of HLLE scars, and I haven’t done anything different.”
There are a couple things to take into consideration, along with the hard water..
One is water change schedule, and because it may be the same now, as it was 3 years ago, that cute little 3” oscar is quadruple that size, and putting out quadruple the waste, but those 50% water changes might be still only once per week.
Results the fish is swimming in fish pee, and fish poop soup, and high nitrates (no matter how great the filtration).
When most people get their tap water, it is 99.999% pathogen free, and close to nitrate free.
As soon as it is dechlorinated, it becomes a great home for nasty bacteria, and the more your oscar pees and poops in the water, the better place it is, for those bacteria to grow, so even with a 50% water change there are 6 days for bacteria to double, triple or more. Many pathogens reproduce at alarming rates.
And here is where the hard water comes into play.
Species that live in soft, tannin filled waters, have evolved (on a cellular level) to live with different bacteria and protozoa, than live in hard water, and evolved to resist those soft water species of bacteria. And tannins themselves are anti bacteria in many cases.
When a soft water fish species, is put in hard water the osmotic pressure, allows hard water bacteria to invade on a cellular level, and cause chronic disease.
I have also heard it said ….
“But my friend raised thousands of discus in hard water”.
Many discus breeders change large amounts of water on a daily basis, sometimes up to 90%, per day, to get good growth.
This is where the 99.9999% pathogen free tap water comes into play.
When those massive water changes are done, beside removing growth inhibiting hormones, and nitrate, they also remove a good portion of those bacteria every day, or even every other day, so bacteria that cause diseases like Hold in the Head are removed, and can’t get a foothold.
Most average aquarists don’t change 90% of the water in there oscar tank, once every week, much less every day.
To give an example of how osmotic pressure works.
When I treat a tank for ick, I add enough salt to bring the salinity (osmotic pressure) to 3ppt. That extra osmotic pressure is lethal to simple celled animals and lyses them.
Most fish are not acutely effected, or killed by that extra osmotic pressure, but it does put chronic low level stress on them, and allows (what would be) normally benign bacteria to enter soft water fish on a cellular level, causing chronic disease like HLLE.
Add an out of the norm osmotic pressure, to high nitrate, and the other stress factors of aquariums like cramped quarters or inappropriate tank mates, and it’s amazing we don’t see even more disease.
Last edited:
