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January 5, 2021 | By 1

by Tom Sarac

Tropical fish: what happens in the wild?

Most fish and invertebrates are ectothermic poikilotherms, meaning their environment dictates their internal body temperature – more generally, they are known as cold-blooded creatures. Considering the stable but still slowly changing nature of tropical climates, native aquatic life requires a consistent temperature, with any changes taking place gradually and in small increments.

Speaking of slight changes, the tropical rainy season is exactly that type of period. The daily downpours of rain, which occur over the span of several months, result in small drops in water temperature. Often, this in turn triggers certain species to spawn, such as Corydoras catfish. It also changes aquatic habitats: within the Amazon basin, for example, the river expands well into the rainforest. Fish such as discus take advantage of that time to spawn as well, given the dense vegetation that becomes submerged and provides both safer refuge and a greater number of food sources for their tiny offspring. Mimicking these natural events and the resulting water conditions are important strategies when attempting to breed some of the more challenging species. Maintaining a consistent temperature within the natural range of tropical fish is a key element to their overall wellbeing and health.

An ounce of prevention is worth a pound of cure

While the diseases that are manifested by the stress fish suffer from sudden temperature changes are generally not difficult to cure, as many tropical fish species can endure them on a one-time basis, repeated fluctuation of temperature is sure to have negative consequences.

The very simple act of glancing at a thermometer on a daily basis is the best preventive tip. There is no understating the importance of doing this, no matter how reliable your heater is: always read water temperature by looking at a thermometer. Do not rely on the temperature displayed on a control knob of a heater. Fluval E series heaters are in a class by themselves, as their digital readout is a result of highly responsive sensors, but even they should be backed up by a thermometer.

Another recommended preventive tip is to keep a spare heater in case your existing unit fails. That way, no matter what the circumstances are, you are prepared to quickly plug in the back up unit with minimal interruption of temperature control.

Make sure to periodically clean the heater tube, ensuring it is free of any algae growth or mineral deposits. Coraline algae growth in marine aquariums can be so quick that you may overlook spots of it starting to proliferate on the glass tube of a heater. To facilitate removing growths like that, simply remove the heater 10 to 15 minutes after unplugging it and soak it in a 50/50 mixture of tepid water and vinegar.

Positioning the heater

To ensure a consistent temperature throughout the entire aquarium, always make sure to position the heater in the path of water flow from the output of your filter system. Avoid placing the heater in an area where there is little to no water movement. When installing a heater, also be careful not to push the end of the tube into the substrate, as this will reduce efficiency as well as increase chances of breakage.

When considering submersible versus clip-on style heaters, the submersible units offer much greater flexibility and almost always represent a better choice. Being submersible, they feature a line showing where the minimum aquarium water level needs to be, while at the same time offering superior protection against water intrusion, resulting in longer and more reliable performance.

How much heating power do I need?

Several factors influence how much heating power is required. An aquarium with strong surface agitation will drive more heat out of the tank, and aquariums with no cover or glass top will allow more heat to escape. In general, 3 to 5 watts of heating power per gallon of water is recommended if the desired water temperature is within 10°F of the room’s ambient temperature. Smaller aquariums lose heat more rapidly than larger aquariums, so a minimum of 5 watts of heating power per gallon is recommended. Larger aquariums – 50 US gallons or more – typically fall into the 3 to 5 watts of heating power per gallon range, but depending on the aquarium’s placement in the home or its setup, it may still require additional heating power.

While an aquarium heater cannot lower temperatures, there are ways of doing so. As was previously mentioned, agitating the water surface of your aquarium and opening or removing the cover or lid will contribute to heat escaping from water. In these situations, unplugging the heater is not recommended, as the unit will remain off until the desired water temperature is reached, at which point it will begin heating and regulating the water once more. The installation of a chiller on larger aquariums is another option when cooler water temperatures are required.

What constitutes a quality heater?

First, a quality heater should consist of a glass tube that is made of a more durable material than just plain glass. One such material is boron silicate, which features a low coefficient of thermal expansion, meaning that it will not crack when exposed to extreme temperature changes. This is highly desirable because, in an aquarium heater, the very hot coil that is responsible for generating heat is only separated from the much cooler aquarium water by the glass tube: the temperature difference is extreme, so the material must be able to withstand these conditions.

Ideally, a heater’s glass tube should also blend in. Large black tubes are obtrusive; reflective mirror tubes, such as those found on Fluval M series heaters, are an innovative way of allowing the heater to blend in with its surroundings. Control knobs and levers should be accessible, easy to use, and responsive.

A quality heater should also quickly and clearly communicate important information to the user. Fluval E series heaters are amongst the best in the industry for this reason: the water temperature is clearly displayed on a large digital display, and whether this temperature is above or below the set temperature is also indicated. The heaters also communicate other key parameters; for example, if the water temperature is off by an unusually large amount, or if the heater is not receiving enough water flow.

The importance of a quality heater and thermometer for a tropical aquarium cannot be understated. When it comes to maintaining the water temperature for your tropical fish, don’t skimp out, invest in their protection, as it can be the difference between life or death.


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