We've been in our new house for around 6 months and have done nothing with the pond we inherited. It's been looked after by the prior owners but now we have no idea how to maintain it. There's no fish but the odd frog and a million tadpoles at the moment. There's no pump (as far as I'm aware!) and seems pretty naturally maintained. Can anyone help with what things we should do? Some sunny weather at the moment means the water level has gone down a bit, and I can see some sludge now....