It is always advisable to check you pond every day, you could find that the water level drops, especially in the hot weather, this will probable be down to evaporation as long as you have not got a leak, just top it up trying to use fresh water.
Try and avoid tap water as this is not very good for fish, if you are constantly losing water then try adding dechlorinator this helps to remove any chlorine in the water,alteratively try to give you pond more shade by introducing a few plants or rocks.
Keeps your eyes open for any rot or dying plants and debris, these seem to decay and can easily block any pumps or filtration system you have in place, Its also a good idea to check the filters quite regularly as this can restrict the flow and the pond starts to get dirty and then oxygen levels can drop which is quite dangerous for any pond fish.
Try to avoid cleaning any bio filters you have with fresh water as this can cause damage to the ecosystem of the pond, again this can be very harmful to pond fish.
Remember clean healthy and well run ponds, give you healthy fish, why waste good money on quite expensive fish just to watch them die.
Return from other maintainence to maintaining ponds