Right, you really need to get some kind of water conditioners. Putting fish in water from the tap can be harmful. Tap water has ammonia in it, that turns into nitrite. These 2 chemicals are extremely dangerous to fish and could kill them. The nitrite then turns into nitrate (notice the spelling) and this is less dangerous. Live plants can absorb nitrate.
When you first got your tank you should have idealy left it without no fish for about 3-4 weeks with the filter on.. with the tap conditioner in it. This sets up bacteria in your filter. When doing your water change you should only do 25-30% so the water still has alot of the bacteria in it. If i was you id go out tomorrow and buy a testing kit, some aqua safe. This is needed ASAP for the wellbeing of your fish!
Hi there CeeJayy, You've got a good deal of the nitrogen cycle story right there, just a few details we could work on some... Its actually the chlorine/chloramines we'd be first worried about in simon's case, because they are potentially harmful to the fish as well as the bacteria and its just a very sensible safety factor to remove them from any fresh tap water. Any given water authority will use one or the other but nearly all modern conditioners now handle chloramines as well as chlorine.
While its true that tap water can have ammonia in it, its fairly rare for it to be very much, still you are correct there can be some. That ammonia, plus ammonia from the fish respiration (yes, they give off ammonia when they breathe!), from fish waste and from plant debris and excess fish food, will be present in the aquarium. In simon's case, after 2 to 3 months, the filter will probably have been populated by the two species of bacteria that will process the ammonia (assuming they weren't killed off by the chlorinated water!) As you've indicated, the first bacterial species will convert ammonia(NH3/NH4+) to nitrite(NO2) and the second species will convert nitrite(NO2) to nitrate(NO3) and then nitrate(NO3) is removed via the weekly water change. That's a short version of the nitrogen cycle story (how the N atoms move into and out of the tank!) Live plants can indeed absorb nitrate(NO3), but prefer to absorb ammonia in most cases and in either case its not a significant amount relative to tank maintenance, so water changes are still needed.
Setting up a tank and running the filter will not prepare the filter with bacteria (called "cycling" the tank) unless there is a significant ammonia source. Common sources are household ammonia (used in a process called "fishless cycling"), fish themselves (in a process that can be dangerous to the fish themselves, called a "fish-in cyclng situation", via decomposing fish food or shrimp/prawns, or via "cloning," where mature filter media from another tank is transferred. The vast majority of the beneficial bacteria live inside the filter within "biofilms" they form on the filter media like sponges and ceramics, they are basically not found in the water and so are not harmed by water changes. The correct percentage of water to change should be determined by other factors like the hardness, pH and temperature match of the incoming water. If the tap water matches well, often 70% or larger water changes (with conditioning and rough temperature matching via your hand) can help save goldfish in small tanks where the filter is not cycled (not the case here hopefully.)
These goldfish should be re-homed as soon as possible (a goldfish grows to more than a foot in size) but if simon plans to then change over to small tropical fish or plans to buy a huge expensive setup for the goldfish, then investing in a good liquid-based test kit would be appropriate and would be the only way to measure the immediate danger to the fish. Until that kit is bought, the only guarantee of not exposing them to permanent gill and nerve damage would be to probably change at least 50% of the water per day.
~~waterdrop~~
oh, and almost forgot! Welcome to TFF guys!
- I only ever get taken seriously in LFS's if i can speak to someone who isnt up their bum, so to speak.. I was speaking to a pets at home manager today, and he was telling me quite alot.) Thanks again.
