Getting Started: Partial water changes

In addition to ignorance of the nitrogen cycle, improper water changes are one of the most common problems with beginning and even long-time hobbyists. Water changes are quite simple, and also quite essential to a healthy aquarium. There are several reasons for this. First, wastes build up even in a fully cycled tank, and water with high levels of nitrate and other wastes needs to be diluted with water containing no nitrate. Second, fish need certain minerals that are provided for them in tap water, and that they can run out of if water is not changed for a long period of time. This is even more important to plants, which require a multitude of micronutriants that are often supplied in tap water. The partial water change is also the time to remove dead and decaying debris and waste from the gravel of your aquarium, which can poison your fish if it builds up too high. Water changes need to be performed every week, or even more often if your tank is overstocked or your tank is cycling with fish in it, but in an established tank properly stocked, changing the water only once a month may be enough. Many beginners when they hear water change don’t notice, or aren’t told, the “partial” part. They think their tank should be routinely cleaned, as in sterilized, so they empty ALL of the water, scrub the decorations and gravel with bleach or even soap, dump all the old filter media and replace that, and fill it up with all new tap water. If you read the nitrogen cycle section of this blog, you realize that this is the worst thing you can do if you want a healthy aquarium. Much in fish keeping seems counter-intuitive to the novice, such as the idea that a bigger tank is easier to maintain and that you want bacteria growing in your tank. The reasons for this should be clear by now though. The more water you change, even if you don’t sterilize your tank, the more stressful for the fish, because even if the source of the water for your tank is the same as always, the water chemistry in a tank is constantly drifting, so to a fish the old water in the tank is quite different from the fresh tap water.

So how do you perform a partial water change? It is very simple. You are changing anywhere from 10-45% of your tank water, depending on many factors such as waste levels, how heavily you stocked your tank, the type of fish you have and water change frequency. You need a bucket -- preferably one with gallon amount graduations on the side -- that has never been used for cleaning chemicals, and a siphon hose with gravel vacuum attachment (see equipment section). Turn off the light and take the light and canopy off of the top of your aquarium. If you have a fully submersible heater that will not be exposed when you take some of the water out of your aquarium, you can leave it on, but make sure you unplug it if it will be exposed below the “fill to” line. A heater exposed to air can overheat and crack. You can leave the filter running, as long as the intake will remain below the water level. Many gravel vacuum siphons have a check valve, allowing you to move the wide end up and down rapidly in the water to start the siphon. If not, simply suck on the end of the tube to start the water flowing. You don't need to suck the water all the way to your mouth for the siphon to work, so don't worry about getting tank water in your mouth; you only have to suck water most of the way through the tube. Even if you swollow some tank water though, it is a little gross but it won't hurt you. Use the gravel vacuum end to suck the junk out of the gravel in your tank, working your way through the tank until all the gravel is vacuumed or you have removed the desired amount of water. If you missed some gravel, simply start vacuuming there on your next water change, and if you still have water to remove when the gravel is clean, you can simply suck the rest of the water from anywhere in the tank. Be careful to not catch any fish in your gravel vacuum tube, as they can be injured if they get caught on the small opening where the water enters the small tube of the siphon. If anything clogs your tube, put your finger over the end of the siphon to stop the flow, or if you have to, blow into the tube to release the pressure.

The perfect time to rinse the filter media out is when you have a bucket of old tank water you intend to dump. You should do this every month to maintain proper water flow through your filter. Never sterilize your filter media as that will kill your biological filter. Simply swish the cartridges through the water, scraping any gunk clogging them off. If you have a sponge, squeeze it in the water multiple times until it looks clear of matter clogging the pores. When the desired amount of water is removed, you can add new, dechlorinated tap water. If you salt your tank, remember that to keep a constant level of salt, you need to add the correct number of teaspoons per gallon you REMOVED, not per gallons that you are adding to the tank. This is because the water that you lose to evaporation is simply water lost; the tank still has all the salt you added since it cannot evaporate. Partial water changes are also the best time to clean algae off of the inside of the glass and off of decorations. Remember that you DO NOT want to remove your fish during water changes. It is much more stressful for them to be taken from their tank to a bucket and back to their tank than to simply work around them. Just be careful not to hit them with anything such as a scrub tool or decorations you are replacing in the tank.

Once the tank is cleaned and re-filled, you can replace the canopy, plug back in anything you turned off and your water change is done!