Coldwater tank filtration

Question
Hi,
I have a 50lt coldwater tank that seems to could up rather quickly, within about 2 weeks of changing about 50% of the water.
I have an under gravel filtration system that was supplied with the tank. I also use an gravel filter but that just makes the water cloudier and can take 2 days to settle back down.
Is there a better way to filter this tank?
Or a safer and more effective way to clean it other than starting again?


Answer
Good evening Mark, thank you for your question.

You say you have a coldwater tank. What you don't mention is, what have you got living in it? If the answer is goldfish, then I must say that only one goldfish is really suitable to live in this volume of water. 50 liters (about 12 US gallons) is the bare minimum for one goldfish. They are very messy, heavy feeders and certainly undergravel filtration alone is not going to cut it! In fact I recommend if you indeed have goldfish, that you remove the undergravel filter from your tank, since this kind of filtration is not recommended for a goldfish tank. It will clog too easily.

Instead, use a hang-on power filter. Get a filter that is rated for 100 liters, double the filtration is recommended in a goldfish tank. You could also get 2x filters rated for 50 liters. You also would do well to have an air driven sponge filter (such as the ones Hydro makes) inside the tank, providing extra mechanical and biological filtration. You can read more about different kinds of filtration here:
http://www.goldfishconnection.com/articles/details.php?articleId=35&parentId=2

There is a much better way to clean a fish tank than breaking it down and starting over. In fact, the cloudiness you describe is due to an interruption in the biological filtration...maybe you vacuumed too much of the gravel at once (it's recommended you only vacuum half at a time) or maybe you rinsed the filter media in tap water. Don't do this! Use dechlorinated water or aquarium water from water changes to clean filter media, it will remove the debris without harming the beneficial bacteria.

Read more here about how to clean a fish tank safely:
http://freshaquarium.about.com/od/fishqa/f/faq0110.htm

If you don't have goldfish, please do let me know, but your problems sound very much like those of someone keeping messy fish (such as goldfish)...other coldwater fish such as zebra danios and white cloud mountain minnows are nowhere near as messy. If you do indeed keep goldfish, please remember these two sites for reference: http://www.kokosgoldfish.com
and http://www.goldfishparadise.com

Wetwebmedia.com has compiled many Q&As about goldfish, including a fine article about goldfish feeding:
http://www.wetwebmedia.com/FWSubWebIndex/gldfshmalnut.htm

Make sure you are not overfeeding and that you are effecting *weekly* water changes of up to 50%, with a minimum of 30%. Two weeks is just too long to go without a water change in a tank of your size! Remember to vacuum the gravel and service the filter at least once every two weeks.

I hope that helps, please write back if you need more help.

Nicole