Originally Posted by leogtr
I have 2 ten gallon plant-only aquariums and I was wondering if I needed the filters that I have working with each. Do they need the water to circulate? or can I just leave them with the lights and no filters? do the plants need fish in there with them or is it okay for the plants to be by themselves?
thank you for your help!
Filters are useful to circulate the water, and this serves a couple of functions. It distributes heat around the tank [though without fish this is not that important], it keeps the water clear by removing suspended particulate matter which could otherwise settle on the plant leaves, and it brings the nutrients in the water to the plant leaves and roots. So ideally, I would have a sponge filter in a 10g plant-only tank. But having said this, I doubt you will have problems without a filter. I had a 10g running for a few months without a filter, it had plants and fish and snails, but I was not happy with the look of it so I added a small sponge filter and the water clarity improved [plants "clean" the water, but the filter "clears" it, two different things]. So, you can go either way.
Fish will add nutrients to a tank, namely CO2, ammonia/ammonium, plus their waste. The latter can be somewhat handled with a liquid fertilizer, but ammonium and CO2 will not. However, there is still the bacteria in the substrate, and if there are any organics down there, which there likely will be, some ammonium and CO2 will result from the bacterial processes decomposing the organics.
I have kept plants in fish-less tanks for months. There were lots of snails in the tank, this helps. I noticed the plants remained alive, but did not grow anywhere as fast as they will with fish. So yes, plants will live in fish-less tanks but grow slower.