I'd like to buy one to fish. Do you want an air pump or a water pump? Is there any difference? How much is the tank 40-20-20?
Mainly A air pump oxygen, B water pump filter and strengthen the water circulation. Of course, thinning down, the pump can also add water, fairy raised nitrifying bacteria, strengthen biochemical filtration and so on.
Submersible pump - circulating filter tanks, ----40 water tank - waterfall filter is enough.Add oxygen pump cylinder with water, fish -- increase the normal weather is not without the addition of oxygen - floating head,
The air pump is used for inflating and increasing oxygen. It is used in the case of more fish.Water pumps are used for filtering and pumping. They are normally used.40 of the cylinder, if only fish, you can buy a multi-functional submersible pump, both filter and beat oxygen.30 or so, you can buy a nice one...
