|
|
Chlorine and Chloramine
The Danger
Frequent weekly or bi-weekly water changes are an important part of keeping a
fish tank healthy and stable. Over time waste products accumulate. And when water
is lost to evaporation, the minerals and waste products are left behind, increasing
their concentration over time. Also, the nitrification process (The filter converting
ammonia into nitrite into nitrate) will slowly decrease the water's buffering capacity. If the
buffering capacity is depleted, the pH can crash very quickly.
Water changes help remove the bad stuff, and help replenish the tank water's buffering capacity.
When adding tap water to a tank for water changes, several things should be done to make sure that you
don't shock the fish. First of all, the temperature of the replacement water should be close the same temperature
as the tank water. Second, and just as important: The water must be chemically safe for the fish.
If you get your tap water from a commercial water system, that water is treated to make sure it's
safe for human consumption. The water is cleaned, and filtered. Then, chemicals are added to
the water to prevent anything harmful from growing in the water while it's in the pipe leading
to your home. Until recently, most water treatment facilities used Chlorine to kill off any
organisms in the water. The small dose of chlorine is safe to drink, but many people notice the
slight chlorine odor. One problem water treatment plants have with chlorine is that it's unstable, and
easily dissipated from the water. This means that the treatment plants need to put in higher levels of
chlorine, so that they can be sure that some will remain in the water when it reaches your home. Recently,
water systems have started treating tap water with chloramine instead of chlorine. Chloramine is a combination of chlorine and ammonia. It's much
more stable than chlorine. It won't dissipate from the water as easily, and it isn't as likely to
combine with other chemicals. But, chloramine isn't as good at killing off the microorganisms in the water as chlorine, so
higher levels of chloramine are often used. Typically, water treatment plants use about 1 ppm of chloramine.
All this hard work and chemistry is important to keep people healthy. But, the same chemicals which keep people
safe can be VERY toxic to fish. Adding tap water with chlorine or chloramine to a tank can
kill off fish quickly. It can also kill off the bio-filter bacteria that keep your tank healthy and happy. So, this water must be made safe for the fish and tank. How do we do this? There are
several common approaches, and their effectiveness varies depending on whether your local water treatment plant
uses chlorine or chloramine. If you don't know which your water system uses, ask them. If you don't know who your water supplier is, the American Water Works Association's List of Water Utility Home Pages can help.
Common treatment approaches
- Do Nothing!
This approach is pretty simple. For small water changes, many people
just add the tap water without treating it first. Any chlorine or chloramine is allow to enter the water.
If you are adding just 10 gallons of tap water to a 100 gallon tank, and you water contain just 1ppm chloramine,
then you will end up with just slightly over .1 ppm concentration in the tank. That's probably not going to do any visible harm.
A couple problems with this approach. First, your treatment plant may occasionally increase the amount of
chlorine or chloramine. So you might be fine 99% of the time, but if the water treatment plant increases the level, and
you add it untreated to your tank, you could suddenly have a bunch of dead fish. The second problem with this
approach is that just because the fish seem fine doesn't mean that the chlorine or chloramine isn't doing some
minor damage to your fish. Over time, this could kill them.
- Aerate/Age the tap water
This approach has long been used by aquarists. Fill a barrel or bucket with some
tap water and let it sit for a day or two. In this way, the temperature will
be close (room temp), and the chlorine will dissipate from the water. Adding an airstone
or powerhead to create water movement speeds the dissipation of chlorine from the water. This is simple, cheap and very effective when dealing with chlorine.
If your water system uses chlorine, this is a great way to go. There might be times when you
need to add some water right away, and don't have any already aged. So that's one problem with this method. The
bigger problems is that this approach doesn't work for chloramines. Thats one of the main
reasons that chloramines are being used instead of chlorine. It's more stable, and won't dissipate as easily. Some report
that aging chloramine treated water for a week will eliminate the chloramine, but several
water treatment websites suggest that isn't always true.
If your water treatment plant uses chlorine, and you decide to use this approach, you might want to regularly contact your water supplier, so that
you are aware of any planned switch to chloramine. Slowly, more and more water treatment plants seem to be
switching to chloramine.
- Chemical Dechlorinators
There are many products sold for aquarium use that are
specifically intended to remove chlorine. Several brand names include: Prime, AmQuel, AP Tap Water Conditioner, Aquasafe Plus, and many more.
These all include Sodium Thiosulfate, which reacts with the chlorine (or the chlorine portion of the chloramine) to form
harmless chloride ions. The chlorine is completely and totally removed. This reaction happens instantly. The tap water doesn't need to
be mixed with the dechlorinator for any amount of time before adding it to the tank. It's safe to just add the dechlorinator as you add the water into the tank.
There is one potential problem if your water is treated with chloramine. As stated above, the dechlorinator reacts
with the chlorine portion of the chloramine. The chlorine is eliminated, leaving the ammonia
free in the water. As you hopefully know, ammonia is toxic to fish, even in low levels. So, if you use a simple dechlorinator
that only contains sodium thiosulfate, you are solving one problem (chlorine) and creating a new
problem (ammonia).
Lucky for us aquarists, our aquarium product companies have a solution. Many of the
dechlorinator water conditioners include chemicals to convert the ammonia into harmless ammonium. Look a a few
labels. My favorite one, Seachem Prime, states: "Removes chlorine, chloramine, and ammonia". Others that I'm sure handle
the ammonia include Tetra "AquaSafe NH/CL Formula", Jungle's "ACE", Kordon's "AmQuel", and Kent's "Professional Ammonia Detox".
If the label doesn't specifically mention that it neutralizes ammonia, then don't depend on it to
safely treat water containing chloramines.
UPDATE
There is an ongoing discussion on APD about Chloramine, and how much of a threat it really
represents. Here is some more info about treating Chloramine with a product that only
deals with the Chlorine:
EPA Guidelines set a maximum allowed level of Chlorine of 4ppm. Most water supplies target 2-4 ppm Chlorine.
Note that 4ppm of Chlorine is actually 5.8ppm Chloramine. (The Chlorine is 69% of the chloramine molecule,
ammonia is the other 31%) So, with a possible 5.8ppm Chloramine, you have 4ppm Chlorine, and 1.8ppm ammonia.
Assuming a 100 Liter tank (about 26g):
If you do a 10% water change, you would end up with .18ppm ammonia.
A 25% water change gives you .36ppm ammonia.
Ammonia toxicity varies based on pH and Temperature, but
in my book anything more than 0.1ppm ammonia is too much.
From a 1995 post here by Neil Frank:
"Then, it follows that short-term concentrations of total ammonia
should not exceed 0.1 mg/l and longer term (4-day average)
concentrations should be less than 0.02 mg/l."
http://fins.actwin.com/aquatic-plants/month.9507/msg00139.html
- Activated Carbon Filters
Using the same technology as the activated carbon filtration
used in many aquarium filters, Activated Carbon can be used to filter the water right from your
tap. Many people use simple carbon filters on their kitchen tap, to remove nasty
tastes and odors from their drinking water. The same filter units can be used
to filter the water before adding it to the aquarium. Many of these tap filters only offically
claim to remove the "taste and odor" of the chlorine, making no promise of how much chlorine is really removed.
Other carbon filter units specifically claim to be able remove
chlorine but the amount of chlorine they remove depends on the quality, size, and flow-rate of the filter, and the amount of chlorine in the
tap water to begin with.
In addition to the effectiveness concerns regarding the removal of chlorine, is the issue of
chloramine. Very few carbon filters can remove chloramine. The chlorine-ammonia bond prevents standard
carbon from removing the chlorine. Some new carbon filter units are now using a special "Catalytic" Activated Carbon.
This catalytic carbon can break the chlorine-ammonia bond, and absorb the chlorine. BUT! They leave the ammonia free, which we've already said is a bad thing.
I've seen one tap-water filter that added a special ammonia absorbing compound (zeolite) in addition to the carbon. But zeolite has a fairly
small ammonia absorbing capacity so it needs frequent replacement, and it isn't found in any common tap-water filters. Without the additional ammonia absorbing compounds, you must use some
other treatment to remove the ammonia.
There are several other problems regarding the use of carbon filtration. First, the effectiveness of
the chlorine removal is highly dependant on the flow rate. Filters will commonly list the recommended flow. One high-quality
filter states "At 1 gpm (gallon per minute), with an input of 3ppm, the output will contain .5ppm". As you increase the water flow thru the
filter, the effectiveness drops. Some filters contain flow-restrictors to prevent you
from increasing the flow above the recommended. In either case, to allow effective filtering, your
flow rate is limited.
Another problem is that the carbon filter can only remove a certain amount of chlorine. After the filter
has treated that certain number of gallons, it's effectiveness is greatly reduced. Some of the more high-tech
filters contain electronic monitors, that inform you when it's time to change
the filter element. But if you keep using the filter past it's stated life, you
are gambling with your fish's lives.
- Other filters
There are several more advanced water filters that are occasionally used in
the hobby. R/O (Reverse Osmosis) and DI (Deionizers). These techniques are
complex, and are not normally used for simple chlorine/chloramine removal. They are used
when you need to remove EVERYTHING from your water. R/O systems are complex, expensive, and the
resulting water normally needs to have lots of chemicals remixed before the water can be
added to the tank. In many cases, R/O systems require other filtration methods to remove chlorine/chloramine
from the water to prevent damage to the R/O system.
Summary
I hope this article has helped educate you about the dangers of chlorine/chloramine, and helped you understand the
ways to protect your fish from that danger. The information in this article came from many hours of research.
Here are links to some of the more informative sites I found during my research:
Article Survey
Your feedback on this article would be greatly appreciated. All feedback is
anonymous, so please, be honest. Your input can help me create better content.
If you have any questions about this article, or if you feel that something is
incorrect or missing, please let me know via email at cgadd@cfxc.com
|
