Every so often, a company will claim to have ‘invented’ a new kind of aquarium which claims to be self-maintaining or self-sufficient, and which need very little (if any) water changes. Even worse is that there are companies selling betta fish in jars with plants above them, and claim that this is also a self-maintained or aquaponic system where the fish and the plant live symbiotically. Here’s just one example:
And then there are the pond owners who maintain that all of their pondlilies and pond plants keep the nitrates down and thus they only need to top-up with water.
Frankly, it’s all a load of rubbish!
Even if we take into account the nitrate cycle and that plants will ‘eat’ and thus use-up the nitrates, no pond or tank is going to have enough of these to keep the nitrates down to a healthy enough level. Goldfish and koi produce far too much ammonia (later converted into nitrites and then nitrates by the beneficial bacteria) for plants to consume.
Don’t get me wrong, plants do help a bit! But not enough that you can forgo water changes.
This has been a point of discussion for me recently, having cleaned out my boyfriend’s pond, and then his grandmother’s pond too. Neither had done much research before and assumed that just because no fish had died recently, their ponds were fine (even if you couldn’t actually see any fish because the pond was so dirty!)
PLEASE! It’s getting warmer (here in the Northern Hemisphere) so please take the opportunity to get outside one weekend and make a big difference to your pond. Have a good clean (click the above link for advice on how we cleaned out two ponds) and a big old water change!
Goldfish Fables 