The other thing I want to mention is that the gold fish, IMO is the most dirty species of fish. (Pirana can make more mess but that's only when you feed them live animals)

Tank Maintenance

Weekly tank maintenance is vital to the health of your fish. For example, if you have read the bit on cycling, you'll know that deadly nitrates can normally only be removed through water changes. Live plants can help some, but for the beginner, this is normally not an option. In addition, if you only top-up your tank's water due to evaporation, minerals present in your tap water slowly build up to toxic levels. Water changes are necessary no matter what your tank set up.

Maintenance usually involves scraping algae, cleaning the gravel/sand/substrate, removing and replacing about 1/4 (25%) of the water, and, if necessary, cleaning filters (please read the instructions below on how to clean your filters before you do it!)

The following list of equipment is necessary to ensure proper maintenance:

• Gravel Vac. This is simply a tube with one end larger than the other, but it is crucial.
• Bucket. Large buckets will make water changes easier.
• Algae scraper. You're gonna get it, so get one of these before algae gets out of control.
• Dechlorinator. You should already have this at hand.
• Tap water.

Here, then, are instructions for weekly tank maintenance. Please note that this should be done weekly:

1. Algae. Get out your trusty algae scraper and begin removing it from the tank sides. Never use a metal scraper on an acrylic tank.
2. Heater. Turn off the heater. A heater without water to conduct heat to will overheat and fail, creating cold and unhappy fish and fishkeepers.
3. Beneficial Bacteria. Depending on the type of your filter, you may need to turn it off. Your goal is basically to keep the bacteria at least submerged in the tank water at all times. If this means turning your filter off and throwing the media (sponges, wool, etc.) in to the tank to float, then by all means, do it. Certain filters (such as hang-on-back AquaClear) can be left running up to a certain point. The important thing to remember is if the filter is left to dry, you will have to re-start your cycling process -- not fun. Please always keep your filter in tank water during maintenance.
4. Vaccing. You can now gravel vac. This will do two things. One, it will clean the gravel of fish waste, uneaten fish food, and other nasties; two, it will remove a portion of your water. Here's how gravel vaccing works:
   1. Place a bucket directly below your tank.
   2. Insert the larger end into the tank until it reaches the bottom; you'll have to keep a hand on this end at all times.
   3. Get a siphon started in one of two ways. Here is the less hygienic way: Suck on the smaller end until water just passes the highest point of the vac tube (you can clasp your hands around the tube if you don't want to directly touch the tube with your mouth). Quickly put the end into the bucket. The more hygienic way is to purchase a self-starter kit. Just put it in the tank and fill the cylinder with water..lift it up and let it start to drain then dip it back in the water and you should have a suction after that. Either way you chose, water will begin flowing from the tank to the bucket without you doing any work. Gravitational potential energy does it for you!
   4. Move the larger end that is still in the tank back and forth through the gravel. Lighter particles such as poo and uneaten food (a sign of over-feeding!) will be sucked into the vac, leaving the heavier gravel behind. Be careful of bottom dwellers such as cories; you may find it helpful to keep a ready hand by the smaller end of the tube to stop the flow of the siphon incase a fish gets sucked up accidentally. But if you are careful, this should never happen.
   5. Once about 20 to 25% of the tank water has been removed, stop the siphon by raising the larger end above the now lower water line.
5. Filter. If you noticed that your filter's flow rate has been reduced in the past week, it is likely due to clogs. Take your filter media and give it a light rinse in the bucket water. NEVER CLEAN A FILTER USING PLAIN TAP WATER, as the chlorine will kill all of the cycle bacteria. You're not trying to make the media look new again (a well-loved sponge will be permanently discolored), but rather just removing scum and large water-clogging particles.
6. Refilling. Double check that no fish made their way into the bucket, then empty out the bucket into your lawn or toilet. Add the appropriate amount of dechlorinator to the bucket, then refill it using tap water. You can adjust your tap-water to the temperature of your tank, or if you have high heavy-metal content in your hot water line, use cold water mixed with hot water from the kettle. Either way, make sure the temperature of this new water is nearly equal to the tank's water.[/i] (Incidentally, this is a good time to rearrange the decor in your tank if you think it is necessary, since you won't have to stick your whole arm into tank-high water.) Carefully add the new water to your tank.
7. Turning everything back on. If necessary, put the filter material back into the filter and turn everything (including the heater) back on. I can't tell you how many times I've forgotten to do this. If it helps, put a stick-note on the front of the fish tank as an in-your-face reminder.

You should now be set. If you like, you can test your water parameters before and/or after water changes to ensure 20 to 25% is enough. If your nitrates are still high, say greater than 60 ppm, you are likely over stocked or your tap-water contains high amounts of nitrates. Complain to you water company if the latter is true.

Thanks to wuvmybetta for the self-starting kit suggestion and Irf for the possibility of metals in hot water notice.

Tank Maintenance

Weekly tank maintenance is vital to the health of your fish. For example, if you have read the bit on cycling, you'll know that deadly nitrates can normally only be removed through water changes. Live plants can help some, but for the beginner, this is normally not an option. In addition, if you only top-up your tank's water due to evaporation, minerals present in your tap water slowly build up to toxic levels. Water changes are necessary no matter what your tank set up.

Maintenance usually involves scraping algae, cleaning the gravel/sand/substrate, removing and replacing about 1/4 (25%) of the water, and, if necessary, cleaning filters (please read the instructions below on how to clean your filters before you do it!)

The following list of equipment is necessary to ensure proper maintenance:

• Gravel Vac. This is simply a tube with one end larger than the other, but it is crucial.
• Bucket. Large buckets will make water changes easier.
• Algae scraper. You're gonna get it, so get one of these before algae gets out of control.
• Dechlorinator. You should already have this at hand.
• Tap water.

Here, then, are instructions for weekly tank maintenance. Please note that this should be done weekly:

1. Algae. Get out your trusty algae scraper and begin removing it from the tank sides. Never use a metal scraper on an acrylic tank.
2. Heater. Turn off the heater. A heater without water to conduct heat to will overheat and fail, creating cold and unhappy fish and fishkeepers.
3. Beneficial Bacteria. Depending on the type of your filter, you may need to turn it off. Your goal is basically to keep the bacteria at least submerged in the tank water at all times. If this means turning your filter off and throwing the media (sponges, wool, etc.) in to the tank to float, then by all means, do it. Certain filters (such as hang-on-back AquaClear) can be left running up to a certain point. The important thing to remember is if the filter is left to dry, you will have to re-start your cycling process -- not fun. Please always keep your filter in tank water during maintenance.
4. Vaccing. You can now gravel vac. This will do two things. One, it will clean the gravel of fish waste, uneaten fish food, and other nasties; two, it will remove a portion of your water. Here's how gravel vaccing works:
   1. Place a bucket directly below your tank.
   2. Insert the larger end into the tank until it reaches the bottom; you'll have to keep a hand on this end at all times.
   3. Get a siphon started in one of two ways. Here is the less hygienic way: Suck on the smaller end until water just passes the highest point of the vac tube (you can clasp your hands around the tube if you don't want to directly touch the tube with your mouth). Quickly put the end into the bucket. The more hygienic way is to purchase a self-starter kit. Just put it in the tank and fill the cylinder with water..lift it up and let it start to drain then dip it back in the water and you should have a suction after that. Either way you chose, water will begin flowing from the tank to the bucket without you doing any work. Gravitational potential energy does it for you!
   4. Move the larger end that is still in the tank back and forth through the gravel. Lighter particles such as poo and uneaten food (a sign of over-feeding!) will be sucked into the vac, leaving the heavier gravel behind. Be careful of bottom dwellers such as cories; you may find it helpful to keep a ready hand by the smaller end of the tube to stop the flow of the siphon incase a fish gets sucked up accidentally. But if you are careful, this should never happen.
   5. Once about 20 to 25% of the tank water has been removed, stop the siphon by raising the larger end above the now lower water line.
5. Filter. If you noticed that your filter's flow rate has been reduced in the past week, it is likely due to clogs. Take your filter media and give it a light rinse in the bucket water. NEVER CLEAN A FILTER USING PLAIN TAP WATER, as the chlorine will kill all of the cycle bacteria. You're not trying to make the media look new again (a well-loved sponge will be permanently discolored), but rather just removing scum and large water-clogging particles.
6. Refilling. Double check that no fish made their way into the bucket, then empty out the bucket into your lawn or toilet. Add the appropriate amount of dechlorinator to the bucket, then refill it using tap water. You can adjust your tap-water to the temperature of your tank, or if you have high heavy-metal content in your hot water line, use cold water mixed with hot water from the kettle. Either way, make sure the temperature of this new water is nearly equal to the tank's water.[/i] (Incidentally, this is a good time to rearrange the decor in your tank if you think it is necessary, since you won't have to stick your whole arm into tank-high water.) Carefully add the new water to your tank.
7. Turning everything back on. If necessary, put the filter material back into the filter and turn everything (including the heater) back on. I can't tell you how many times I've forgotten to do this. If it helps, put a stick-note on the front of the fish tank as an in-your-face reminder.

You should now be set. If you like, you can test your water parameters before and/or after water changes to ensure 20 to 25% is enough. If your nitrates are still high, say greater than 60 ppm, you are likely over stocked or your tap-water contains high amounts of nitrates. Complain to you water company if the latter is true.

Thanks to wuvmybetta for the self-starting kit suggestion and Irf for the possibility of metals in hot water notice.

If I can add my 2p worth, over the last year or so, I've started preparing my freshly dechlorinated buckets of water the night before the change. I also use narrow tubing to put the fresh water in the tank. Obviously it takes longer to top up the tank, but I'm sure it's better for the fish to become slowly accustomed to the new water.