Please visit our Sponsors

Related FAQs: SAEs in the Aquarium Garden, Algae Eaters

Related Articles: Loricariids/more than Plecos, Otocinclus

/The Aquarium Gardener Series

Will the Real SAE Please Swim Forward?

Epalzeorhynchus and Crossocheilus et al.; or Minnows as Biological Algae Controls; In Search of the Elusive SAE's (Siamese Algae Eaters)

By Bob Fenner

Are you?

"Pssst, hey buddy, wanna buy the world's best freshwater algae eaters?" "Hey, come over here and take a peek." "No, not the cheapy "Chinese" algae eaters, sheesh, they're not even from China. No and not those, they're flying foxes, nor those phony SAEs, look closer..."

Ah yes, wherefore art thou, magical Siamese algae eaters? Those Asian masters of live plant aquarium algal eradication. Heck, they'll even tackle some of the "untouchable" black and filamentous red forms. Downsides? They do jump out of tanks like no-tomorrow similar to the other "minnow-sharks". And are they hard to find? The related genus of flying foxes and a "false" Siamese algae eater are much more readily available, easily confused and not nearly as serviceable to aquarists; oh, yeah, poorly handled batches can die easily...

If "true" SAEs are the best algae eaters for live plant tanks, how come we don't see them offered more often and promoted for the job? Where can you, even should you plop the money down for a few? What are their husbandry requirements? Could you displace Bill Gates by mass breeding, rearing and selling these suckers?

Before giving the heave ho to existing earthworm farming, baseball cards, or mink-raising get-rich schemes allow me to help you define what these fishes are, their selection, use and possible propagation.

Classification: Taxonomy, Relation With Other Groups

Most of the fishes we will cover here are members of the largest family of fishes, the minnows, Cyprinidae. With some 210 defined genera and 2,010 species you might imagine this super-group is further sub-divided, and though many cyprinids are of interest to us (Rasboras, barbs, danios, freshwater "sharks", bitterlings) well leave it to you to delve into their taxonomy.

For perspective, and to introduce the "Chinese" algae eater (in a separate family, Gyrinocheilidae), the minnows share the Order Cypriniiformes with them and such other notable families as the freshwater suckers (Catostomidae), the loach family (Cobitidae, of some 18 genera and 110 species!), and the river loaches, Balitoridae (formerly Homalopteridae), a weird group of sucker- and loach-like fishes from Eurasia that have yet to be exploited as aquarium specimens.

Natural and Introduced Range

Minnows en toto are almost entirely freshwater (a few venture into brackish), and are found all over Africa, North America and Eurasia; absent in South America. China and Southeast Asia have the greatest diversity, with some 475 members in 23 genera. That's a lot of minnows.

Of the three genera we're dealing with, the two minnows are spread over Southeast Asia, Malaysia, Indonesia (Epalzeorhynchus), and the "Chinese" algae eater Gyrinocheilus which comes from northern India and central Thailand.

Selection: General to Specific

The first and foremost task the would-be purchaser must surmount is finding and identifying which minnows are which. Crossocheilus and Epalzeorhynchos species (which we'll forthwith refer to as SAE's and flying foxes), are wild-collected, a few species occupy the same waters, and what's more their points of gathering mix and match a few species over their geographic ranges. The long and short of this is that you'll have to learn the principal types discerning characteristics yourself (some popular aquarium reference works offer inaccurately labeled images) in order to tell which species you're dealing with.

Further confusing the issue is the fact that of fishes collected from the locality of the true SAE, there is at least three species of Crossocheilus; all appearing quite similar as live aquarium fishes (able to be discerned by careful examination of mouth structural elements as preserved specimens or with good/great photographs). All three-plus bear some variation of the "defining" characteristics listed below, and there is varying usefulness of the different species as algae eaters.

Principal Species Offered In the Trade & How To Tell Them Apart:

Just what's in a name anyway? Plenty. All three of the following genera are ofttimes labeled Siamese algae eaters, flying foxes, even Chinese algae eaters; let's clear this up.

Epalzeorhynchus; the original "flying fox" genus. Don't let it throw you that the "true" SAE, Crossocheilus siamensis used to belong to this genus (it was called Epalzeorhynchos siamensis), and is listed as such in even recent works. We will abandon the confusing "Java flying fox" for the common name "true SAE".

Epalzeorhynchus like the following two genera, have elongated cylindrical bodies, with a dark body stripe, and underslung mouth, and attain about six inches maximum length. The not-so-big criterion separating the two genera is the presence of a movable but rigid lobe at the corners of the mouth of Epalzeorhynchus (illustration).

The Flying Fox, Epalzeorhynchos kalopterus (Bleeker, 1851) has 1) A smooth edge to its horizontal body band, 2) The dark band extends through the base of the caudal fin (the peduncle) to its fork, 3) Its dorsal surface is smooth appearing, with no emarginations between the scales, 4) Its fins have distinct coloration, generally yellowish, with some black and white highlights.

Crossocheilus, are the SAEs. For contrast/differentiation with the flying fox the true SAE (C. siamensis (Smith, 1931)) has 1) A zig-zag uneven appearance along the upper edge of their dark body band, 2) The horizontal bar extends onto and through the middle of their caudal fin, 3) Its dorsal surface appears cross-hatched due to the dark margins around each scale, 4) The fins are almost colorless except for the aforementioned caudal ribbing. The real thing above...

Bigger PIX:
The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size.

The "false Siamese algae eater' (often offered as the 'colorful flying fox'), probably a Paracrossochilus species is far more common than the true SAE (C. siamensis), and much more attractive, much more like the flying fox. It's comparative characteristics: 1) The lateral body band is smooth, not zig-zagged in appearance, 2) This band does not extend beyond the base of the muscular caudal peduncle, 3) The dorsal surface is not cross-hatched in appearance, 4) Its fins are distinctly yellow-hued.

Gyrinocheilus, the "Chinese Algae Eater", Gyrinocheilus aymonieri (Tirant, 1883); neither from China (from Northern India and Thailand), nor much of an algae eater as adult (becomes a "fish sucker", killer as it rapidly grows), bears an overall dark cross-hatched pattern on a light brown body as a juvenile. As they grow this species lateral markings coalesce into a definite horizontal bar. Gyrinocheilus has a distinctive sucker mouth, with a modified gill cover opening allowing respiration without using it as a water intake.

Maybe it is divine justice that I had to catch so many of these fishes as a retail clerk in fish stores in the U.S., though I'd tell of alternatives and their ultimate downsides, I was rarely successful in dissuading customers. As a lad in the trade in Japan we used this species as feeders to piranha and other piscivores; a more suitable function.

"Other Algae Eaters" offered in the trade abound, especially should you cater to a distributor, retailer that dabbles in "contaminants" (mis-shipped, miscellaneous, unidentified/able other fishes that make their way from wild-collected sources). There are Garra (Pictured at right), Paracrossochilus, other Crossocheilus, Epalzeorhynchus and more that occasionally come into domestic markets. Much of their systematics is in doubt, and the aquarist would do well to inspect any and all purchases closely with definitive photographs and descriptions of the species you want on hand.

Environmental: Conditions


Crossocheilus and Epalzeorhynchus live in streams of moderate water movement amidst plant-filled stream edges. They appreciate current and rock/wood strewn planted confines as well.


None of these fishes proves touchy to a wide range of water conditions given initial health and proper acclimation. Temperatures in the seventies to low eighties, pH 6.5-7.5, to moderate hardness is fine.


As seems reasonable with so many species living in such close, complex relationships developed over such long geological periods of time... there is a Crossocheilus minnow (C. cobitis (C. pseudobagroides is a synonym)) that is a mimic of a catfish (Pelteobagrus ornatus, Family Bagridae); a form of Batesian mimicry where the minnow apparently accrues a non-predatory advantage by appearing like the less tasty, more spiny Bagrid cat.


Should be brisk, rendering good, clear oxygenated water and a pleasing current. My favorite choices are outside canister and inside power filter types of size that can be used without allowing "jump-out" gaps at the systems top.


For best showing, both flying foxes and SAEs should be maintained in a (large) well-planted system in a small grouping (3,5,7...). You will find they shoal loosely, working algae over often resting in a loose troupe.

Without having to resort to moving your SAEs, place them at no more than one per 15 gallons.

Behavior: Territoriality

Both SAEs and flying foxes can be or become quite antagonistic toward their own and related species. For this reason they should all be placed simultaneously and not overcrowded. I stand by my suggestion of about one per 15 gallons maximum for SAEs.

Epalzeorhynchus can become true tyrants of a system with growth, much like the minnow "sharks" of the genus Labeo. I would not attempt more than one in a system of less than thirty gallons, and then keep my eyes on them.

Other minnow "sharks" as mentioned can become terrors in their own right. Either keep them apart from these algae eating minnows or be on your guard should harassment turn to war.


If I haven't made the point clearly enough, let me restate it here, THESE FISHES JUMP OUT! In addition to making sure your aquarium lid is complete, it is a very good idea to lower the water level a few inches the first week or so, to prevent exuberant "flying" out of the aquarium and onto the floor.

This cautionary remark applies to mere netting and transport of these fishes as well. How many times have I heard/seen them bolt from nets, bags, specimen containers, buckets...? Too many.

Predator/Prey Relations

Ready to give the boot to all those armored South American sucker-mouth cats variously called Plecos/Plecostomus, whiptail, twig cats, (Family Loricariidae)? Not so fast, bucko. A notable trait of all the minnow members and the Chinese algae eater is their palatability; humans eat them and so will your larger, piscivorous fishes. Should you have large cichlids, other wide-mouth fish-eating livestock, you may well have to stick with that ugly Pleco, or scrape algae yourself.

Reproduction, Sexual Differentiation:

As for many minnow species, Epalzeorhynchus and Crossocheilus show little external difference between the sexes. Females are slightly fuller and overall larger during spawning season.


All these fishes have poorly developed gas bladders and thus either swim in constant motion, often at a pronounced angle, or rest utilizing their mouth and paired fins on plants, other decor or the bottom.

Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes

Though all the fishes listed here will do some work on keeping algae in check, with the best to worst being Crossocheilus, Epalzeorhynchus, Gyrinocheilus, all will learn to take "regular" types of fish food. You should take care to just provide enough to their tankmates, as these facultative algae eaters can and will become lazy cleaner-uppers should other fare be more available.

Should your system be too clean, intentional green food should be offered. True SAEs rarely do real damage to live plants as they cleanse them of debris and algal growth, but some aquarium gardeners endorse the use of "feeder" soft floating plant material (Lemna, Limnobium) for ready munching.


The best algae eaters, bar none, for the planted freshwater aquarium are members of the genus Crossocheilus, the true SAEs. The biggest barrier to their use is finding and differentiating them from the far more common Epalzeorhynchus and false SAEs.

The small South American Otocinclus are also excellent algae eaters for plant tanks, but more touchy and limited in their tolerance to captive water conditions.

For aquariums without plants or with large fish-eating tankmates, the armored catfishes of the family Loricariidae still rank supreme. The misnamed Chinese algae eater Gyrinocheilus should either be left in the wild or relegated to "feeder" status. It becomes a bogus cleaner and outright peaceful-fish-killer as it grows.

Bibliography/Further Reading:

Baensch, Hans A. & Rudiger Riehl. 1993. Aquarium Atlas, v.2. BAENSCH, Germany. 1212pp.

Banarescu, Petru M. 1986. A review of the species Crossocheilus, Epalzeorhynchos and Paracrossocheilus (Pisces, Cyprinidae).    Travaux Du Museum d; Histoire Naturelle "Grigore Antipa". v.28, 141-161.

Boruchowitz, David E. 1999. Good fish, bad fish (the Chinese Algae Eater). TFH 4/99.

Castro, Alfred D. 1996. Algae al fresco: Exactly which algae eater really likes to chomp down on this stuff? AFM 12/96.

Fenner, Bob. 1994. Guerrilla acclimation methods, or acclimating: My way. FAMA 10/94.

Frank, Neil & Lisa Sarakontu. 1995. Algae eating cyprinids from Thailand and neighboring areas (Crossocheilus). The Aquatic Gardener 8(2):3,4/95 and AFM 4/96.

Hunziker, Ray. 1992. The sharks that aren't. TFH 4/92.

Kutty, Vinny. 1993. Algae eaters. The Aquatic Gardener 6(3):5,6/93.

Nelson, Joseph S. 1994. Fishes of the World, 3d ed.. John Wiley & Sons, Inc. NY. 600pp.

Riehl, Rudiger & Hans A. Baensch. 1982 (sixth ed. 1996). Aquarium Atlas, v.1. MERGUS, Germany. 992pp.

Riehl, Rudiger & Hans A. Baensch. 1996. Aquarium Atlas, v.3. MERGUS, Germany. 1104pp.

Sarakontu, Liisa & Neil Frank. 1996. Siamese algae eater and it's relatives. FAMA 5/96.

Schonfelder, Wilfried. Undated. The Java flying fox- An unbeatable algae eater. Aquarium Digest International #26

Graphics Notes:

Some images showing the three principal species discussed:

0) C. siamensis, the true SAE; you have images already.

1-3) The false SAE, perhaps Paracrossochilus vittatus clearly showing the termination of the lateral band before the caudal, its smoothness and yellow finnage.

4) E. kalopterus, the flying fox as golden juvenile and washed out grey adult.

5,6) G. aymonieri, the often obnoxious "Chinese" algae eater, showing the broken body band, cross-hatched overall brownish body coloring.

7) An illustration showing the differences between 1) Crossocheilus (c. oblongus) and 2) Epalzeorhynchus (e. kalopterus); the chief contrast lies in the flap labeled fr, the frenulum, rigid movable lobes which Crossocheilus lacks. (from Banarescu)

8) Is this our mystery fish, the false SAE? What I believe to be, Paracrossochilus vittatus (also from Baranescu).


Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: