Is There Such a Thing as "Freshwater Shock"

[DISCUS STU]

I've read about this for years but always doubted that changing water parameters from deficient / bad to good or excellent could damage fish.

After all, would a person sustain damage from going from bad air to good air?

Is there anything to this?

[yogi]

There is some truth to this and a better definition would be stress than shock. I doubt what I'm about to say would apply to discus because they would probably die from the deteriorating conditions first. Most fish do not need the pristine conditions we keep our discus in and they can tolerate lower water quality.

So here is the example you have a fish tank of common fish and over time you let the water deteriorate like not doing water changes, possibly some overfeeding and not cleaning your filter. This all happens over a period of time lets say a few months. So since this is all gradual your fish slowly adjust to it. There not real happy but they are living and eating. So now for some reason you say I'm going to do as close to a 100 percent water change as possible. You try to match the water conditions you have and you go ahead and do the giant water change. Your fish are now stressed and shocked because of the drastic change. The organic and mineral content change of the giant water change now makes your fish sick and they die. You would of been better off doing several 20 percent water changes over a few weeks and improving the water quality slowly over time than all at once.

Dr. Ed Noga explained this to me several years ago at an ALA convention. It sounded strange at first but when you think about it, it makes sense.

[William1]

It makes perfect sense. Thank you for sharing that. Consistency in your cleaning and water change schedule is paramount. Not go all gung-HO for three weeks then slack off for four. Then try to get it back. Your fish are in a completely closed environment. Keep your water fresh and clean and steady. It makes perfect sense.
Like the Dead reference. Broke Down Palace has always been a fav of mine. Well, I like it all. Cheers, BK

[Filip]

As far as i have read on this subject I believe that this shock happens because of the sudden change of the ammonia and PH values .

Water in non maintenanced tanks lowers its pH values over time due to organic compounds decomposition , making the deadly ammonia ,No2 No3 presence more sustainable and less toxic for the fish.
With a big and sudden WC ,PH levels goes up to normal again but there are still deadly ammonia amounts presence in the water which kills the already weakened fish .
This is the same reason why gradual adjustment of water ,pouring drop by drop of a newly shipped discus or any other fish is less reccomendable than drop and plop method.

[DISCUS STU]

Taking into account that sudden downward PH swings can be dangerous to Discus health, I've never really seen upward PH swings affect my Discus and I've had them go from the low 5's to the 7's within a few minutes, I think the term applies more to the idea that suddenly adding good healthy, less toxic water low in ammonia, nitrites, nitrates, can somehow be injurious to fish health.

The term "Freshwater Shock" is something that I've seen since the 90's but I'm wondering if it's really a viable term.

[Poppa Ryno]

Osmotic shock

[Jason.M]

Yup correct term is osmotic shock. Quick and dirty of it is: the amount of dissolved solids changes drastically causing osmotic regulatory shock. Lots of late night (boring/technical studies) reading on the web about it. I did quite a bit of reading on the subject in order to better educate myself to help keepers of large cichlids that showed up on our(another) forum with sick fish due to bad husbandry. Always start with small water changes to avoid this. As stated earlier though, discus would probably succumb to the poor conditions before the water quality got so bad as to cause this from a large water change.

[pitdogg2]

As far as i have read on this subject I believe that this shock happens because of the sudden change of the ammonia and PH values .

Water in non maintenanced tanks lowers its pH values over time due to organic compounds decomposition , making the deadly ammonia ,No2 No3 presence more sustainable and less toxic for the fish.
With a big and sudden WC ,PH levels goes up to normal again but there are still deadly ammonia amounts presence in the water which kills the already weakened fish .
This is the same reason why gradual adjustment of water ,pouring drop by drop of a newly shipped discus or any other fish is less reccomendable than drop and plop method.


Osmotic shock


this ^^^^^^ agree 100% folks who age their water would be more susceptible I would think because they may not use any water conditioner and whammo ammonium goes to ammonia when PH goes about 7.0 and they die.

[CliffsDiscus]

We called this Freshwater Allergy in the SF Bay Area,

Cliff

[bluelagoon]

Also when water gets old it depletes/deceases in PH;this causes "some" of the beneficial bacteria to die off.Then,wammy a large water change;the PH increases.The bacteria multiply quicker and the good bacteria hasn't caught up yet=bacteria bloom and increased ammonia.