Practical Fishkeeping Diploma - Week 5, Day 4

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Here's the fourth of a five-part series of lessons to guide new aquarists through the basics of fishkeeping.

Week 5, Day 4: Feeding

Fish need food for energy and metabolic processes, as well as protein and nutrients required for muscle growth, tissue repair and egg development.

Incorrect feeding can cause nutritional diseases (Diploma, part 4). As well as these, the aquarist needs to avoid underfeeding or overfeeding.

Underfeeding can lead to emaciated or weak fish, poor egg production, inability to regenerate damaged tissues, stress, lowered immunity and eventual death.

Overfeeding can be problematic in several ways. Uneaten food decomposing in the aquarium produces more ammonia than food that has been eaten by fish and subsequently utilised for growth and energy. Excess food consumed by fish will lead to elevated amounts of ammonia excretion, placing a burden on the filter.

Uneaten food can lead to outbreaks of snails, planarians, copepods, and bacterial or algal blooms.

Understanding the feeding behaviour of a species is essential to gauging how much food to offer it. Fish may be opportunists or grazers.

Constant grazers (such as marine seahorse) cannot retain food stores and need near constant feeds throughout the day. Hardcore opportunistic predators, like Red tail catfish, might gorge on a single giant meal and then not feed for weeks, until the meal has been digested.

Most aquarium fish are casual opportunist feeders that will gorge when food is available. This means that they will feed to excess given the opportunity.

Ammonia is released relative to how fish feed, and grazing fish release it differently to predatory fish. Grazers excrete ammonia constantly, while predators produce ammonia in large, intermittent spikes, whenever fed. A tankful of predators fed at the same time will experience more drastic ammonia fluctuations than a tank filled with grazers.

Community fish require two to three small feeds a day. For the majority of species, offer as much as they will eat in 90 to 120 seconds, and then stop until the next feeding schedule. Ideally, fish should receive food as a percentage of their bodyweight daily, which would involve weighing the fish.

For day to day maintenance, most fish require 1% of their bodyweight in food daily. For fast growth, tissue repair or egg development, this can be raised to 2% bodyweight daily. At the extreme, 3% bodyweight daily may be offered to fast growing fry

Fish have low energy requirements compared to similar sized terrestrial dwelling animals, such as mammals. Fish need to neither generate body heat (as mammals do) nor resist gravity (their swimbladders make them neutrally buoyant), saving them considerable energy.

Note the mouth position of a fish, as discussed in module 3. Ensure that species can access the type of food offered — floating food for surface feeders, sinking food for bottom feeders — and that it is of the right size for their mouths.

Click here for next lesson: Cleaning

How to gain your diploma: Once all the course modules and revision pages have all been posted online, we will open a link to a website that allows you to take your free online exam. If you pass the exam, you will digitally receive your very own Fishkeeping Diploma, to show that you have successfully completed the course, and which is yours to display on the wall near your aquarium, hang in your fish house — or keep somewhere safe where you can take it out and just look at it from time to time.

Note: The Fishkeeping Diploma is not a formal or accredited qualification and should not be confused with the type of diploma presented by colleges, universities and other educational establishments.

Further reading from our sponsors

Guide to regular fish care

Guide to fish nutrition

Routine aquarium care

Feeding your fish