Water Changes      
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Friday, 13 July 2007

A water change is the act of removing detritus while exchanging old tank water with clean saltwater. We all know we need to perform this task, however the When, How and the How Much are open for great debates amongst the hobbyists themselves.

Water Changes


 The three main reasons behind the water change  are to:

  • Remove a portion of the pollutants from the water
  • Dilute the remaining pollutants with the replacement water
  • Replace minerals utilized by the tank. There is no need for “bottled supplements” if you are performing your water changes routinely. Any supplements you do use should be for a component that is testable and should not be added blindly.

The When and the How Much I mentioned above is open to an individual’s interpretation. Watching your tanks parameters can help you decide what is best for you and your tank. If in the 3rd week you find your nitrates climbing, the once a month routine is not going to work for you. If you pH starts to flatten after 2 weeks, you probably have a buildup of organics waiting to be removed with that water change. Although it’s true this can be caused by a multitude of factors, if you see your water quality typically declining in between water changes…. you aren’t doing  them often enough. However often and whatever amount, if you find a routine that works for you, stick to it. I have found that a 10% weekly water change has kept my water parameters in check and my fish and coral nice and healthy.

So, what are we trying to remove from our tanks? Basically, uneaten food and the byproducts of that food once it is processed. In short, every organism in your tank produces some form of waste, nitrogenous, or otherwise.  When it comes to water changes, many people consider only fish waste, however, the waste produced by corals and other invertebrates should also be considered.  The expelled waste continues to be processed further into byproducts including nitrates, phosphates and silicon.  If left unattended, these compounds may reach problematic levels. For instance, nitrates and phosphates act as a fuel for nuisance algae.

Another contributor to excess nutrients is uneaten food. These leftover food products break down almost the same as fish waste.  For this reason, it is important to know what we are feeding our tanks and how much.  We sometimes love our fish too much, which leads to over feeding and ultimately turns into red slime, hair algae, and high levels of nitrates, ammonia and phosphates, to name a few.

The act of the water change itself is not the simple task of sticking a hose into the aquarium, removing some water and replacing it with clean saltwater. Removing detritus should be one of your main goals.

Another thing one must consider is that all water changes are not created equal. No matter how good of a job you did cleaning the tank, removing the detritus and exchanging the water, if the water you are returning to the tank is not “top notch” your efforts will be in vain. Chemically treated (dechlorinated) tap water is quickly losing favor with many saltwater aquarists. It simply contains too many nutrients (such as nitrates, phosphates and silicates) as well as many unknowns (like copper and other heavy metals) to be of much benefit. It is best to start out with good quality Reverse Osmosis/De-ionized (RO/DI) water. Home RO/DI units can be bought fairly inexpensively, and once you’ve tried one you will never go back. These units work by separating contaminants from the water by forcing the water through pre-filters, which remove sediment and carbon to remove chloramines. The water then finds its way to the membrane, further removing molecules above a certain size. Wastewater water containing these contaminants is washed down the drain and a fairly clean water is produced from another line. Some people stop the filtering here, at which point their water would be just referred to as Reverse Osmosis (RO) water. The TDS reading at this point will be dependant upon the rating of your membrane. Most people choose to add a canister containing de-ionizing  (DI) resin will produce water that has a TDS reading of 0-1ppm. A reading of 2 or greater suggests something is not functioning properly or the DI resin is spent. Just a couple of notes about RO/DI produced water; they can be high in carbon dioxide and low in oxygen. It must be aerated AND buffered before use as either evaporation replacement or to make saltwater


An RO/DI system can be bought relatively cheaply.


I would recommend looking into as many options and DIY ideas as possible to facilitate the performance of the “dreaded” water change.  Every little thing you do while doing a water change can affect the quality of your tank and affect the way you feel about doing water changes. I often hear people saying it takes to much time to perform a water change, so they put it off, ultimately leading to an emergency water change that could have been avoided.  I spent many months perfecting my method of a very easy, and very healthy water change.

Converted siphon: I converted a short siphon into a long siphon so my hand stays out of the tank and dry.



Salt bucket, heater and thermometer: I use a salt bucket to mix my new salt water and a heater and thermometer so I can match the temperature in the tank. This way I won’t shock my corals or fish.



Pump and hose:  When I mix my salt water in the bucket I use this pump to mix the water, once the salt is mixed and adjusted to the right temp and salinity I turn the pump off and insert one end of the hose onto the pump and the other I clamp to the top of the tank and plug it in. The one disadvantage of this is you have to pay attention to the water level in the DT (display tank) and the bucket. If the water level gets to low it can burn the pump up and if the pump keeps pumping it can overflow the DT.



Let’s start the water change.

Some people may be never give thought to the process of mixing the salt with the water. There's no difference if you add the water to the bucket that has salt in it or if you add salt to the bucket that has water in it, right? Well actually..... wrong. The full volume of water must be in the container first and the salt must be added last. The high concentrations of salt elements, as the water is first poured onto the salt, can create some reactions that later can prove to be a problem with calcium, alk and mag levels. First, you want place the salt into your bucket or container.  I keep three 5gallon food-grade cans full of filtered water at all times.  This is for emergencies and of course water changes. Once the water and the salt is in the bucket I take my pump, heater and thermometer into the water with the pump facing down.  Plug everything in and let it sit.  My heater is set to 80 degrees because my tank is 80 degrees and you want to match the temperature.  Once these steps are complete I let the bucket sit anywhere 5 hours to over night.  Remember to place a lid on the bucket so no foreign matter can get into the container.

Once the bucket has been mixed, temperature adjusted and the salinity stable, you can start cleaning the tank.

I usually start by cleaning the glass, overflow and miscellaneous equipment in the DT. Remember when cleaning sponges, and other such material, not to clean them all at one time. This will greatly reduce the biofiltration available in your tank. Clean them one at a time. Once this is completed you can start cleaning your sand bed and rock work with the siphon.  The same idea applies to cleaning the sandbed as it does to cleaning the sponges. Don't clean the entire bed, but only about 1/4-1/3rd to prevent noticible disruption to the biological filter. I use a small siphon because the flow is low and I can reach into little holes in the rock work.  I like to use a 5gallon bucket to measure how much water I am pulling out of the tank. This is because I don’t want to pull out more than I can replace.  An aquarium mat made for such applications can prevent water from absorbing into the floor.



Drymate Aquarium Cleaning Mat.

Once everything is clean I unplug everything in the new saltwater bucket and insert my tube onto the pump. Then with the other side of the hose I clamp it in the DT so it won’t move and then plug in the pump. I usually aim the tube at my Mag-Float so it will disperse the flow and won’t stir up any sand and harm any corals.  Wait until the bucket gets low, unplug the pump and your done.  Once the water is in the tank I like to let it sit for a hour or two and measure the salinity and calcium and adjust as needed.  During this wait I monitor the corals and fish health visually to determine everything is ok.

Remember, our pets cannot take care of themselves and we need to take extra steps to keep them comfortable and healthy in their environment. Rather than survive we need to make sure they thrive.

Last Updated ( Saturday, 14 July 2007 )
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