If you’ve been an aquarium keeper for any significant length of time, you know that unexpected things can appear in your aquarium seemingly overnight. You may not know where they’ve come from, but suddenly you’re faced with overwhelming numbers of “alien” invaders in your tank, creeping, crawling and swimming all over. Your immediate instinct may be to search for a quick chemical solution to eradicate the unsightly pests, but isn’t it safer for your fish and the aquarium habitat as a whole to solve the problem naturally? We discussed eliminating the causes of some of these critters as natural remedies in other articles, but this time we’ll take another approach…the possibility of finding and adding natural predators to the pest species you’re struggling with. It’s important to keep in mind that though these creatures have been effective in the tanks of other hobbyists, you can never predict the behavior of an individual fish and you may not get the results you’re looking for. Also remember that these fish have to be compatible with the habitat you’ve created and with the other fish in your tank…if you introduce any neew fish or invert to your tank, observe them closely to make sure all of your fish are getting along.
Whether you have live plants in your tank or not snails can appear in your tank and quickly boom in population. While they have their benefits as algae eaters and detritivores, they can become a nuisance if the numbers aren’t kept in check. Generally, for common snails we recommend botia loaches including Skunk Loaches, Clown Loaches and YoYo Loaches. These fish like to indulge on young snails and snail eggs, so they can get you ahead of the problem. However, they can be pugnacious and even a little aggressive in some cases, so they may not be a good idea in a tank with very small or docile fish. True Siamese Flying Fox fish are another great solution, if you can find them in the trade. If you’re plagued with Malaysian Trumpet Snails, your options may be more limited. These snails have much tougher shells than the common little snails that sneak in on live plants, and they can only be ripped out of the shell by specialized eaters with very strong mouthparts. While the loaches may be able to handle very small Trumpet snails, larger versions will be too tough. Some cichlids, including several Julidochromis species develop a taste and talent for eating snails, and C. rhodesii is also a known specialized feeder for trumpet snails.
Planaria are tiny flatworms that look like little blobs on surfaces in the aquarium. They may be any variety of color, and often take on colors of what they eat. When disturbed, they may flutter away like little flakes, settling into every rock and crevice in the tank, but you’ll see them on the glass again, especially when the lights are turned on in the morning. Planaria tend to occur in aquariums that are frequently overfed and not adequately cleaned. While these flatworms are generally harmelss to fish, there are species that are parasitic and/or predatory that may hitchhike into the tank with fish and inverts. They are all a little creepy and they can explode in numbers fast, even if your overfeeding isn’t severe. Typically, cleaning the aquarium and addressing the overfeeding issue will dramatically reduce the planaria population. Fortunately, there are quite a few pretty community fish that are happy to eat these squishy little invaders, as well. Gouramis, Paradise fish and other anabantids may take a particular interest, but other predators include guppies, mollies, platys, angelfish, and Dwarf cichlids, particularly Pelvicachromis. These fish love to browse through the substrate and should keep an average population of planaria under control.
Hydras are related to anemones and corals you would find in saltwater environments, and they resemble a polyp or anemone with a sticky base and multiple tentacles. Like these distant cousins they possess the ability to sting, and can even kill eat tiny fish and shrimp. As with planaria, these pests tend to occur in tanks with less than ideal feeding and maintenance regimes. A strict feeding and maintenance routine may also prevent blooms and help to get the numbers of these little stingers under control. Blue Gouramis have a reputation for eating hydra, as do paradise fish, so these predators are beneficial and attractive. Other recommended eaters include mollies and larger pond snails when they are in season.
Nematodes are the tiny, thread-like white worms that may also appear in a “dirty” tank. They swim in a wiggly, “s” pattern when disturbed. As stated repeatedly, if your overfeeding problem is fixed and the tank/gravel is cleaned frequently the numbers of these creatures will usually stay within manageable numbers. These worms are so small that they are ignored as prey by most fish, but if your community is kind enough, there are several micro-predators that will seek them out as food. These include Boraras (micro-rasboras) and the tiny yet beautiful Scarlet Badis (Dario dario).
Daphnia, Amphipods and other bugs
If you’re on the opposite side of the spectrum with a very clean and healthy tank, you may see tiny crustaceans like Daphnia, Amphipods, Copepods and other harmless crustaceans free-swimming in the water of your aquarium. Generally these are great things to see in the tank! If you have a population of these critters, you have a natural food source thriving in the tank to offer your fish. Many community fish will be happy to help you keep these animals in check, too many to list! Keep doing what you’re doing and reap the benefits of providing your fish with a fantastic dietary offering.
Blue Gourami image referenced from wikipedia and originally posted by Gourami Watcher
Malaysian Trumpet Snail image referenced from wikipedia and originally posted by Dennis L
Daphnia image referenced from wikipedia and originally posted by Hajime Watanabe