Originally Posted by grace1234
I have a 2 1/2 year old healthy freshwater tank which is about 110 litres (sorry, im in the uk, not sure about gallons!!) with some fantail and common goldfish in it. I was just wondering if you should replace the substrate at all? I just have gravel which is about an inch and a half deep, which is obv regularly cleaned with a vac during my water changes. But is there ever a need to replace it/ take it all out and clean the bottom of the tank?
Thanks in advance!
If the water chemistry in your 28 gallon tank is stable, you don't need to change anything. Standard gravel is fine. I'd recommend changing half the tank water every week or so. Goldfish are very high waste producers and you want to keep the water as pure as possible to keep your fish and any plants healthy.
Everything in the tank water will eventually dissolve. So, by removing and replacing a large volume of the water every week or so, you'll romove the toxins that dissolve in the water. Vacuuming isn't really necessary and the material that settles to the bottom dissolves and nourishes your plants.