Catfish of the Month Right Arrow November 1998 • Article © Ian Fuller, uploaded November 01, 1998



Smudge Spot Cory - Corydoras similis   Hieronimus, 1991

This catfish of the month is introduced by guest aquarist Ian Fuller, a self confessed "Corydoras Nut"; Ian has spawned over 40 species of Corydoras in his considerable time keeping members of this family. Ian has also contributed 3 excellent line drawings of this species' fry development you cn see in the breeding information section. Over to Ian...

The trouble with Corys is that if you put a group of say C. similis ( 6 or 8 ) together in one tank they'll act one way, move them into another identical set up and they'll act in a completely different one. When I first got my C. similis they were as busy as beavers. When, after a couple of weeks, I put them into a larger tank, they went to ground and just huddled under the heater. They emerged only to forage.

I tried various things to liven them up, raising and lowering the temperature, as well as water changes using warmer and cooler water. All to no avail. Resignedly, I put them back in the tank that they were first put in -and would you believe it - they went and hid under the heater. I let them be.

They became a little more active only when live food went in; white worm, tubifex or daphnia, one of which they were given at least once a week. Although largely inactive, all fish looked in fine condition, and the females in particular appeared rather plump.

After two weeks without water changes I did what I call my "classic water change": 80% of the water is removed and replaced with fresh water at least 7 to 10 degrees cooler. The cooler water is returned fairly slowly via a small spray rose on the supply pipe. There I go giving all my trade secrets away. Well some of them anyway! Two days after the water change they spawned. Only one female took part and she laid twenty eggs, which turned out to be infertile. A month later I used the same trick again, and with the same result, only this time the female laid about thirty eggs that also turned out to be infertile. Now an infertile spawning is one thing but two on the trot is something else. Nevertheless, after another six weeks I went through the same procedure, but, crucially, with water only 5 degrees cooler.

"Bingo!" 28 fertile eggs were laid. After the spawning was complete the adult fish were removed and released into their original tank. They were visibly more active and less secretive than before. Also one or two plants, in this case Java fern and or Java moss, seemed to make them happier.

Though that was in 1993, I am keeping C. similis again and find that they are just the same. I am about to put my current group into a tank higher up in the fish house to find out whether slightly warmer water will make them a little more active.


Copyright information for the images used in this article can be found on the species' full Cat-eLog page.

Jump to next section Cat-eLog Data Sheet
Scientific NameCorydoras similis  Hieronimus, 1991
Common NameSmudge Spot Cory
Type LocalityTrib. of Rio Madeira, vicinity of Ariqumes, Rondonia, Brazil.
PronunciationKory DOOR ass - sim ill iss
EtymologyCory = helmet, doras = skin. In this case it was incorrectly used to mean armour (cuirasse) instead of skin in allusion to the dual rows of plates that run along the flanks of this genus. Latin similis = like alluding to the similarity of the colouration of this species to Corydoras ourastigma.
Jump to next section Species Information
Size 60mm or 2.4" SL. Find near, nearer or same sized spp.
IdentificationCorydoras are identified by their twin rows of armour plates along the flanks and by having fewer than 10 dorsal fin rays. They are most commonly confused with the other genera in the sub-family, namely Brochis, Scleromystax and Aspidoras.

C. similis is the round nosed ''version'' of the long snouted C. ourastigma. The smudged marking at the base of the caudal fin separates it from other head-spotted species that have a distinct spot marking instead.
SexingFemale is fuller (when viewed from above) and larger.
Jump to next section Habitat Information
DistributionRio Jamari, tributary of the Rio Madeira, East Rondonia, Brazil
Amazon, Middle Amazon (Solimoes), Madeira (click on these areas to find other species found there)
Amazon, Middle Amazon (Solimoes), Madeira, Jamari (click on these areas to find other species found there)
Show it on a map (Click the map-icon to show/hide map of species distribution)
pH5.6 - 7.0
Temperature21.0-27.0°C or 69.8-80.6°F (Show species within this range)
Jump to next section Husbandry Information
FeedingFlake, tablets. Live food such as whiteworm, bloodworm, brineshrimp and tubifex (sparingly). Frozen bloodworm is more easily supplied and seems to bring on growth in sub-adults very satisfactorily.
FurnitureOther similar Corydoras, dwarf cichlids and tetras. A robust species that will adapt to larger peaceful tankmates.
CompatibilityA perfect citizen.
Suggested TankmatesIdeally keep with dwarf cichlids and tetras. A robust species that will adapt to larger peaceful tankmates. Keep in groups of at least six.
Breeding1. A ratio of 2:1 males to females has been successful at a pH of 7.2 and water at 76F which was reduced by approximately 5-6 degrees the day before spawning took place. It was back up to 76 when they began to spawn.
2. The spawning followed the typical ' T ' mating clinch, where the female nuzzles into the side of the male at a point just behind the pectoral fin. The male then clamps the female by her barbels (hence the need for good barbels, poor barbels means poor grip and possibly poor fertilization). Once the grip is complete both fish seemed to tremble for a few seconds, during this time the female deposited two 1.8mm eggs into a pouch made by clamping her ventral fins together. The female then broke away from the male and proceeded to find a suitable place to deposit her eggs. Altogether 28 moderately sticky eggs (out of a scale of 1 to 10 the these were 3) were laid all on the tank sides, all at various levels.
3. All the eggs were fertile and hatched in 4 days. 2 days after hatching the fry were free swimming and given pre-soaked powdered flake. This was followed by alternate small feedings of either brine shrimp or micro worm.
4. Fry Development is pictured above. The fry grew rapidly and at 7 days were 6.2 mm, at 14 days 9.0 mm, in 1 month 12 mm, after 2 months 16.4 mm, and after three months 21.0 mm. Adult colouration in 10 weeks.
5. After the spawning was complete the adult fish were removed, and the water treated with a few drops of methylene blue (1 drop per gal) to protect the eggs from fungal attack. Once the fry had hatched the water was changed at a rate of about 20% per day, for 5 days, removing the methylene blue concentration.
Jump to next section Further Information
ReferencesZ. Fischkundev. 1 (no. 1) - pp39 - Fig. 1
Registered Keepers(1) mikey, (2) Keithj, (3) racer36, (4) Coryologist (k: 13), (5) Yan, (6) Barracuda518 (k: 6), (7) Richie Hell (k: 2), (8) certan, (9) Daragh (k: 125), who also notes: "Includes about 100 week old fry.", (10) NEONCORY (k: 24), (11) amygoodness, (12) fulvioander (k: 2), (13) Carp37 (k: 6), who also notes: "sadly all died within 3 days of each other due to a disastrous experiment with a sand substrate- had been growing well up to that point", (14) AmLi (k: 16), (15) Mazer, (16) glenny, (17) gem400 (k: 10), (18) foffo (k: 8), (19) MatsP (k: 6), (20) alexmuchtar, (21) thelivelylady, (22) scat35, (23) Gry, (24) gismo5001, (25) Olivier, (26) NHL (k: 4), (27) Birger Amundsen, (28) sarae, (29) jar (k: 4), (30) reticulata, (31) behhl (k: 2), (32) worldwide73, (33) fjack88, (34) Boromark, (35) Kampfer, (36) ranmasan (k: 6), (37) FuglyDragon (k: 6), who also notes: "1 very successful spwn to date, approx 30 fry raised", (38) thejudgement (k: 3), (39) Gretesam, (40) tcmfish (k: 2), (41) Devin (k: 11), (42) jørn henning flåten, (43) donishi, (44) rodpam, (45) SHEAG35 (k: 32), (46) corydoras, (47) fishpimpin, (48) Rainyfly (p: 2), (49) Nabobmob1 (k: 6), who also notes: "Cf Similis", (50) Phreatobius (p: 2), (51) boyneburn, (52) jp11biod, (53) Dee (k: 6), (54) sheldon (k: 6), (55) jpod, (56) SHEAG (p: 2, k: 4), (57) coryla, (58) wgtaylor, (59) rhibear (k: 4), (60) Mark Roesner, (61) christiansen (k: 29), who also notes: "Two spawing intervals per year. Frozen Bloodoworms heavy diet increases the egg numbers. Very good hatch rate in mix 3:1 of RO and tap water . TDS ~230 ppm . Alkaline ph", (62) SergenTuncer, (63) reefdive, (64) KansasGuppyGuy (k: 10), (65) Rainbow, (66) donpetty (k: 5), who also notes: "Housed with a C. polystictus.", (67) Rita Aspevik (k: 5), (68) AquariumLover04 (k: 7), (69) MHS, (70) matti2uude (k: 6), (71) ars (k: 19), who also notes: "Spawning group", (72) BigToys (k: 2), (73) mace, (74) kim m, (75) tjudy, (76) CaliCory (k: 3), who also notes: "2 of the 3 seem to be well bonded with all 3 swimming together but the 2 separating off from the group from time to time. All fish are being fattened up in preparation of future spawning. Will be picking up 3 more in another week or so.", (77) leej24 (k: 5), (78) pleco_breeder (k: 6), (79) lasteeves (k: 6), (80) miku (k: 5), (81) anthonyking, (82) gossei (k: 13), (83) mgamer20o0, (84) Vess, (85) estherevans, (86) mpedersen (k: 20), who also notes: "Keeping one mixed group, and a second separate sibling group, in hopes of future breeding with mixed genetics for a vigorous line.", (87) darr3ll, (88) Jass, (89) Zzyzx85, (90) Thoth (k: 4), (91) crazyjock (k: 5), (92) duxallinarow, (93) rmc (k: 2), (94) Rummage, (95) Valb68 (k: 11), (96) Lee Meadows, (97) Supercorygirl, (98) mani29 (p: 3, k: 2), (99) cfa (k: 10), (100) fishdoc313 (p: 2, k: 9), (101) Ozboy (k: 10), (102) lilu (k: 2), who also notes: "More shy than other corys and don't socialize with others.", (103) TKL (k: 7), (104) Ingvald Arne Meland, (105) mark24, (106) camtang, (107) jodilynn (k: 2), who also notes: "Very lovely, distinct little cory, cohabitating with a Peppered Cory and a Trilineatus.", (108) irshprncsk (k: 3), (109) slayer5590, (110) cjerrom, (111) madattiver (k: 12), (112) Lewis m (k: 17), (113) Zulan, (114) irishman710, (115) benma (k: 11), (116) Gerald CapeTown, (117) SeanL (k: 6), (118) RolandNL (k: 22), (119) Xaim (k: 5), (120) Mvinyl (k: 6), (121) rizla75, (122) joshuasmith94, (123) aqua_maniacs, (124) Narwhal72, (125) DJay, (126) fishy1 (k: 2), who also notes: "2 Died", (127) fishfarmer (k: 35), (128) Guppy09, (129) los66 (p: 3), (130) 4evercories (k: 5), (131) Per Jensen, (132) matte s, (133) Junglejason, (134) fishiephil, (135) Coolcorycats, (136) scandicman, (137) Biulu, (138) Maxpedley, (139) Medievalmum (k: 2), (140) Tony4143 (k: 8), (141) dennis84, (142) Samaki, (143) Gormets.

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Breeding Reports(1) christiansen (b: 56), (2) Zulan (b: 51), (3) Nabobmob1 (b: 49), (4) Valb68 (b: 44), (5) rmc (b: 44), (6) Mvinyl (b: 43), (7) Vess (b: 42), (8) TKL (b: 29), (9) Narwhal72 (b: 29), (10) RolandNL (b: 13), (11) donpetty (b: 8).
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Last Update2005 Mar 12 00:00 (species record created: 1998 Nov 01 11:22)

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