To dechlorinate.. or not to dechlorinate

Oz fish guy

Jack Dempsey
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Jan 23, 2018
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So i have been wondering.. say my fish gets sick. Ich or sunken belly or what not. Can i keep the fish in plane old water to eliminate the bacteria/parasite thats infecting the fish.. i wonder this because we put all types of funky things in our water to keep it free of bacteria. So if tap water is potentially bacteria free, if i kept a fish in bacteria killing water would the bacteria inside the fish or outside the fish die.. ya know what i mean guys?
 

xDestro

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I would think the chlorine would not be particularly healthy for the fish
 

Itsadeepbluesea

Goliath Tigerfish
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I don't know for sure, but I'd be inclined to agree with xdestro, long term I think the fish would see ill effects from the chlorine.
 

Oz fish guy

Jack Dempsey
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Yea i get that but ive seen fish live and breed in chlorinated tanks. My local pet shop for example.
 

Oz fish guy

Jack Dempsey
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Im just wondering for the short term. Ick for example. Could ick live in tap water? I dont think it could, so in theory would could tap water kill the bad infecting the fish
 

squint

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Oct 14, 2007
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Chlorine is very reactive and will be neutralized by combining with organics. That's why people with chlorine in their tap water can often get away with small water changes without dechlorinator.

Tap water isn't sterile. Not even close. The EPA limit for E. coli and fecal coliforms is 5%, not zero. Protozoans like Cryptosporidium can easily survive in tap water.

Chlorine and chloramine are much more dangerous to fish than microorganisms.
 

duanes

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Although low levels of chlorine/chloramine eliminates bacteria, those same levels often do not work on protozoa like ick. They (ick) have impermeable shells that protect from the oxidizing effects of compounds like chlorine. Cryptosporidium is a good example akin to ick, and why many water companies have added ozone with chlorine.
Low levels can at times disable newly emerging protozoa, but when a water facility use chlorine as a disinfectant, the concentration is quite high at the initial injection point, enough to create a residual throughout the entire water distribution system to kill bacteria, so that initial concentrated blast will kill protozoa, but will also kill fish.
 

RD.

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According to Edward Noga, a professor at NC State that is considered an expert in the disease & health of fish, chlorine levels as low as 0.10 mg/l (which is common in many tap water levels) can be accutely fatal in aquaria that has low levels of organics. Others have found residual chlorine levels as low as 0.05 mg/l to be toxic to certain species of fish.

There has been a TON of work done in this area over the past few decades, by a number of researchers, such as Tompkins & Tsai (1976) for anyone that is interested in understanding just how toxic both chlorine & chloramine can be in a closed system that contains fish.

Unfortunately the LC50 (survival time) of most tropical species of fish placed under various levels of chlorine/chloramine has yet to be established, but the bottom line is both substances are highly toxic to most aquatic organisms.



From the EPA ....



http://www.epa.gov/chemfact/s_chlori.txt


V. ENVIRONMENTAL EFFECTS

A. Toxicity to Aquatic Organisms

Chlorine has high acute toxicity to aquatic organisms; many toxicity
values are less than or equal to 1 mg/L. Twenty-four-hour LC50
values range from 0.076 to 0.16 mg/L for Daphnia magna (water flea)
and from 0.005 to 0.1 mg/L for Daphnia pulex (cladocern)
(AQUIRE 1994); 48-hour LC50 values range from 5.3 to 12.8 mg/L for
Nitocra spinipes (snail); and 96-hour LC50 values range from 0.13
to 0.29 mg/L for Oncorhynchus mykiss (rainbow trout), from 0.1 to
0.18 mg/L for Salvelinus fontinalis (brook trout), and from
0.71-0.82 mg/L for Lepomis cyanellus (green sunfish) (AQUIRE 1994).
Papillomas of the oral cavity in fish have been associated
with exposure to chlorinated water supplies (NTP 1992).

Low level chlorination (0.05 to 0.15 mg/L) results in significant
shifts in the species composition of marine phytoplankton
communities (HSDB 1994).
 

Itsadeepbluesea

Goliath Tigerfish
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According to Edward Noga, a professor at NC State that is considered an expert in the disease & health of fish, chlorine levels as low as 0.10 mg/l (which is common in many tap water levels) can be accutely fatal in aquaria that has low levels of organics. Others have found residual chlorine levels as low as 0.05 mg/l to be toxic to certain species of fish.

There has been a TON of work done in this area over the past few decades, by a number of researchers, such as Tompkins & Tsai (1976) for anyone that is interested in understanding just how toxic both chlorine & chloramine can be in a closed system that contains fish.

Unfortunately the LC50 (survival time) of most tropical species of fish placed under various levels of chlorine/chloramine has yet to be established, but the bottom line is both substances are highly toxic to most aquatic organisms.



From the EPA ....



http://www.epa.gov/chemfact/s_chlori.txt


V. ENVIRONMENTAL EFFECTS

A. Toxicity to Aquatic Organisms

Chlorine has high acute toxicity to aquatic organisms; many toxicity
values are less than or equal to 1 mg/L. Twenty-four-hour LC50
values range from 0.076 to 0.16 mg/L for Daphnia magna (water flea)
and from 0.005 to 0.1 mg/L for Daphnia pulex (cladocern)
(AQUIRE 1994); 48-hour LC50 values range from 5.3 to 12.8 mg/L for
Nitocra spinipes (snail); and 96-hour LC50 values range from 0.13
to 0.29 mg/L for Oncorhynchus mykiss (rainbow trout), from 0.1 to
0.18 mg/L for Salvelinus fontinalis (brook trout), and from
0.71-0.82 mg/L for Lepomis cyanellus (green sunfish) (AQUIRE 1994).
Papillomas of the oral cavity in fish have been associated
with exposure to chlorinated water supplies (NTP 1992).

Low level chlorination (0.05 to 0.15 mg/L) results in significant
shifts in the species composition of marine phytoplankton
communities (HSDB 1994).

Wow! awesome response, thanks for the info!
 

Niki_up

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I’m just going to put my own experience here, (just a side note, I have made almost every mistake possible when I started keeping fish)

I had a tank, water, filter and one fish...combined all 4 items immediately and watched a horrible death (It was instant) Then learned about dechlorinating water,

Ich treatment is cheap, like $6-$7 Walmart , not worth losing a fish over!
 
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