1、 Fish tank heating rod

The fish tank heating rod is a commonly used tool in fish farming, mainly used to heat up and prevent excessive temperature difference in water temperature. However, the fish tank heating rod is a tool that needs to be used carefully, and if not used properly, it may cause serious problems such as "boiled fish" or fish tank bursting.

（1） Heating rod selection

1. The heating rod can be divided into temperature control heating rod and non temperature control heating rod according to whether it controls the temperature. The temperature control heating rod can be divided into two types, one is to control the temperature directly with Bimetal, and the other is to detect the temperature with thermistor.

(1) The simplest method is to wrap the resistance wire around a ceramic tube and place it in a heat-resistant and waterproof glass tube without temperature control. The wire is connected to the power supply through a waterproof sealant cover. Common specifications include 50w, 75w, 100w, 125w, 150w, and 200w, which can be directly immersed in water for use. This type of heating rod is generally priced below 10 yuan due to its simple production and low cost. However, it has been gradually eliminated from the market due to its inconvenient use. This kind of heating rod is mainly used to heat clean water before changing water in the fish tank, and is usually used with a thermometer.

(2) The Bimetal temperature control heating rod is the most common heating rod in the market, which integrates temperature control! Its working principle is also very simple, that is, a Bimetal is placed inside the heating rod as a switch. Because the materials used on both sides of the Bimetal are different, the expansion coefficient is different when the temperature changes, so that the metal sheet can swing according to the temperature change. By utilizing this, it can automatically disconnect when the set temperature is reached. The advantage is that the installation is relatively convenient, the circuit is simple, beautiful and economical, and the work reliability is high. The disadvantage is that the close distance between the Bimetal switch and the heating rod often causes the internal temperature of the heating rod to reach the set temperature, while in fact, the heating is turned off before the water temperature in the fish tank reaches the set temperature. The phenomenon we often see is that the heating rod stops heating for a while and then starts heating again after a while. Generally, the price of domestic Bimetal temperature control heating rod is between 15-40 yuan. The Bimetal is the control core of the heating rod, and it is also the main difference between fake and regular products. Poor quality Bimetal is prone to fatigue during use, which leads to the failure of Bimetal to turn on or off the heating rod with the change of temperature, and then the tragedy of the fish tank will happen!

(3) Thermistor detection temperature type heating rod. After signal amplification, the heating rod that is controlled to turn on or off is often referred to as an external cylinder temperature control heating rod or a split temperature control heating rod. Its working principle is that the temperature control system controls the water temperature inside the cylinder through a thermistor probe in the water outside the cylinder, and heating is carried out when the temperature control system is separated from the heating system. This heating rod has the advantages of fast heating and accurate temperature control. It can place thermistors and heating rods at relatively long distances, which just overcomes the shortcomings of Bimetal temperature control heating rods. But his shortcomings are also very obvious. Firstly, there is an extra wire for the thermistor, which is more complex to install. Secondly, if the thermistor accidentally leaves the water surface, it will continuously heat up, resulting in a tragic fish tank. But now, in response to this drawback, some heating rods have added a thermistor off water power alarm function, and many temperature controllers use liquid crystal display temperature control. The price of ordinary heating rods for temperature control outside the cylinder ranges from 50 to 150 yuan.

2. Heating rods are also divided into glass heating rods and metal heating rods based on their material.

(1) The glass heating rod is generally provided with a explosion-proof glass shell, which has the characteristics of low price and wide application range, and can be used in various Aquarium. Shortcomings are easily broken. If used in a large fish tank, it must be equipped with a protective cover to prevent damage from the fish. Generally, fake and inferior heating rod glass has poor quality and is more prone to breakage.

(2) Metal heating rods are generally made of stainless steel shells, which have the advantages of being sturdy, durable, and textured. However, the disadvantage is that certain corrosive environments, such as seawater tanks, cannot be used. Generally, fake and inferior metal heating rods use iron shells to impersonate stainless steel shells, which are prone to rusting.