the unexpected

^^dragonfly nymph make pretty neat pets on their own, 
but are a serious threat to small fish and shrimp.
^^notice the wing sheaths, or 'buds' just behind the head.
Dragon nymphs don't have external gills like damselflies.
Fishless ditches and ponds not connected to 
natural waterways are the best place to release dragons. This prevents the 
accidental release of aquarium pathogens and parasites into the wild.

^^damselfly nymph. note the 3 gill appendages
^^emerging damsel. The wing sheath is visible just behind the head. 
Damselfly nymphs are less dangerous than their larger cousins, but will still prey on 
larval fish and slow-moving fry. They'll eat small shrimp, too.

^^water fleas are great fish food. Completely harmless and fun to watch.


^^hydra viridis (green hydra) riding a baby ramshorn snail. 
Although they appear sessile, hydra can swim and "inch worm" their way around the aquarium. Green hydra are not a serious threat to aquarium inhabitants, except maybe to day old shrimp. Other species of hydra can hurt (they sting) or kill small fish and young shrimp. Hydra don't die from old age. They're in the same phylum as jellyfish and sea anemones.

Seed shrimp (ostracods)
 ^^ostracods feed mainly on diatoms

^^seed shrimp can appear black in certain lighting

Water mites
 ^^all water mites are invertebrate parasites at some stage of their life cycle. Some become detritus feeders as adults but most continue to feed on invertebrate hosts - like maybe your shrimp or 
daphnia cultures. (photo credit:
 ^^mites are a little less than 1/2 mm. These killiefish fry are 4mm. (photo credit:
 (photo credit:

Leeches and flat worms
 ^^planaria, extended position, dorsal view, out of water. Note the diagnostic arrow shaped head.
 ^^in motion
^^Seen out of water, this flatworm pulls itself along something like an earthworm. In the water, they are graceful gliders, paper-thin, moving on microscopic cilia over the barest hint of surface.
^^against the glass they look white or pale gray. 
^^not adverse to the company of others

^^leech (photo credit: Kameko Walker)

^^Found in almost any damp place with organic debris, including the soil of your house plants and sometimes even in damp bathrooms, springtails are common residents of the water surface and floating plants. They do an excellent job of eating microbes, molds, mildew and fungus from floating plants, exposed driftwood and even the water surface. Small fish actively hunt them, providing food and activity. Also useful in terrariums.

Snails: the four "pest" species

The four most commonly encountered species of 'pest snails' are all useful aquarium guests. None eat healthy live plants (ramshorns will if starving, the others most a't); they all eat algae from plants and glass; they make excellent janitors, cleaning up left over food, dead/sick plant material and dead fish; and they behave in entertaining ways. People hate them as a matter of aesthetics. The exception to all this love is in the spawning tank. Snails eat fish eggs, and can ruin a breeding project within hours.
^^3 of the 4. left to right: small pond (Radix sp.), tadpole (Physa sp.) and
ramshorn (Planorbis sp.) Pond snails have triangular antennae, tadpole snails 
have longer, thread-like antennae.

^^not to be confused with the giant ramshorn snail from the apple snail group, ramshorn snails are an elegant, if prolific, addition to aquarium fauna. Flesh can be pink or dark. Shell colour also varies.
^^(left) small pond snails multiply quickly when there's food around. (right) small pond snail laying eggs. Unlike their cousins the giant pond snail, small pond snails don't eat healthy live plants.

^^Malaysian Trumpet snails (aka MTS) are highly variable in colour and markings. They're also mostly nocturnal. Since they're a burrowing snail, they help keep the substrate fresh.
^^not all snails and fish mix well. These endlers graze relentlesly on snails.
 ^^duckweed is nutritious and useful. And a total pain in the... It can get thick enough to interfere with gas exchange, block light and choke filters
 ^^and make a mess of other floating plants like this pennywort  There are a lot of ways to remove duckweed from floating plants, all of them tedious. Netting works, but you can kill a lot of fry that way. Use a fine net for best results- baby duckweed is small enough to pass through a regular net.
 ^^dunk 'n sieve. Possibly the safest for fry and shrimp, this method allows you to check for bicatch before discarding the duckweed.
^^use a clear plastic container. Push into the water until part of the lip goes under. The water rushing in pulls duckweed with it, while the other, larger plants stay behind. Check for fry or shrimp, then empty into a fine mesh sieve held over the aquarium.
^^eventually, you get results.
 ^^some turtles, like this Cooter named Yurdle, eat duckweed like candy
(photo credit: KimR. You can see more Yurdle pix at CAC)
 ^^so do these guys (photo March 2012)
  black beard algae
^^corydoras forage in a lush growth of black beard algae
 ^^pop eye
^^scoliosis long fin zebra danio aka glofish, showing scoliosis behind the head (left), heterandria formosa (right). Scoliosis can be age related, genetic (usually from inbreeding), dietary or  bacterial (dirty water). Severe cases should be euthanized (scoliosis is a painful condition) but fish with milder cases should be separated and allowed to live out their days. Fish with scoliosis should not be bred.
 ^^swim bladder disorder Common in goldfish with constipation, swim bladder disorders also affect other fish, like this Norman's lampeye. Typically caused by bacteria as a result of dirty water. This one shared a tank with bristlenose catfish fry, which produce high levels of waste. Obviously, not a good combination. This one recovered fully. "Dirty water" is a loaded term; I use it here to include a variety of situations, anything from short term filter interruption to heavy bioload and/or poor maintenance.
​ Spend a little time researching the remedies you use. For example, Panacur and No Planaria are both toxic to snails​. Copper is toxic to shrimp, snails and other invertebrates. Here are a few to get the list started: Malachite green and here (comes with a strong warning to pregnant women) Methylene blue Fenbendazole (sold as Panacur, Safe Guard)

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