Hook up wires - cost

I recently started looking to automate my aquarium.

My initial prototype consists of the following:

  • Arduino Uno board
  • Solenoid valve per tank, 2 tanks are being controlled for water inlet
  • Ultrasonic Distance Sensor HC-SR04 for finding the water level. 2 of them; 1 per tank
  • Relay control board to control the solenoid and water pump

My question is this. I find that I'm running long hook up wires from my ultra-sound sensor to the Arduino. The cost of the hook up wire is working out to be quite high.
I'm planning to get a servo for a fish feeder. I'm concerned that the cost of the hook up wire to run from the Arduino to two servos is going to be quite high.

Is this a typical scenario for everyone?
The cost of hook up wires to sensors becoming an fairly big component of the project cost.
For wires from the relay board to the solenoid valves, the costs doesn't seem to be so high.

Don't mount them so far apart ?

How much is this wire costing you ?

@Radio shack, it works to about $9 for 75 feet.
The HC-SR04 sensor is roughly about 12 feet from the Arduino. There are about 4 wires that need to be hooked up between the HC-SR04 and the Arduino. That takes almost the entire bundle of $9 to connect the sensor to the Arduino.

The Arduino is at a distance as it needs to control two large aquariums.
Is there any other way to avoid this cost?

You'd need to consider all the issues about running low voltage sensor wires that far, but you can get ethernet cables with more than 4 cores in them for well under a $1 a metre.

I have heard about using Ethernet cables but forgot about them. Thank you for reminding. Great idea!
What sort of issues will I encounter when the hook up wires tend to be long?
Is there a wire length limit that I should be aware of?