aquarium and pond answers, information, articles, resources

Freshwater, Marine, Sick Fish, Lighting, Baths

Our Facebook Page to Follow: Aquarium/Pond Answers Facebook     DONATE

This is a unique resource for answers, help, & advice to aquarium and pond questions not found elsewhere; With regular posts & article updates.

In our research; we use aquaculture, horticulture, medical, & university research to compile many of our articles.

  See our AQUARIUM ANSWERS DIRECTORY page for topics by category.  

Our Recommended Lighting for highest efficiency professional planted/reef aquariums: "AquaRay Lighting"

SEXING FISH, Stimulating Fish Breeding Behavior

SEXING FISH; The differences between males and females (if any).
By Carl Strohmeyer-PAMR 40+ years experience
Updated 1/22/19

I will first point out that the ability to relatively easily sex fish depends on the fish; and for many newer fish keepers sexing can be very difficult.

I would also like to point out that although some articles here at Aquarium Answers are intended to be more in depth, THIS ARTICLE is intended to just cover the BASICS and advanced aquarists will need to seek further information elsewhere.
I provide several links to other sites and articles for more expanded information, please check them out as well

Although information about the breeding of fish is not the main intention of this article, I will provide a few basic factors to consider for many fish developing into a breeding condition (where by "sexing" of the fish is more likely to be successful too).


Important Fish Breeding "Stimulants";

Important Fish Breeding "Water Condition Basics";

Simply put, maintaining good water conditions is a must, this includes 0 ammonia or nitrites, low nitrates, a stable pH, at least some positive mineral electrolytes (some fish need more than others for positive breeding conditioning).

Often successful breeding is performed in bare, no substrate aquarium; this in part aids in the ability to vacuum and wastes as soon as it falls and limits the possibility of devastating Saprolegnia outbreaks in fish or eggs.

Another key point is while many breeding fish prefer at least some quiet calm areas to breed or rest, at least SOME filtration MUST be present. I base this on the FACT most breeders as well as my breeding of fish have been in tanks with some sort of filtration. Generally speaking, an air driven Sponge Filter is your best choice for this.

A Resource for:
Aquarium Sponge Filters

See Also:
*Aquarium Nitrogen Cycle
*Aquarium Chemistry; The Importance of Maintaining Positive Calcium Ion levels
*Freshwater Aquarium Care



Male and female Platy, pineapple sword

In Livebearers such as platys the male has a short tube called gonopodium in place of the anal fin, while the female has a normal triangular anal fin.

Guppies more transparent bodies (although many other light colored livebearers are similar here) are easier than many livebearers to see fry development inside the female.

Gravid female guppy, giving birth Signs that your guppy or other livebearer is about to give birth include a large belly, a box like look from the front view, and a darker gravid spot which is under the pregnant females tail, which many identify as a stained glass window where the fry come out.
As the babies near birth you can sometimes see eyes of the unborn fry as tiny black dots.
Click picture of guppy to enlarge

The gestation period in livebearers, which the interval between fertilization and live birth can vary, however as a generalization this time period is about 4-6 weeks at 78 F. The size of the brood can also vary greatly.
Most livebearers prefer water higher in mineral ion content and although salt is not required by most livebearers, it can be helpful as well.
Keep optimum conditions including proper mineralization as well as supplementing their diets with frozen/live/FD foods along with quality flake, crumbles, & conditioning foods (I would strongly suggest foods high in spirulina such as Spirulina 20 as well as ultra premium staple diets such as "Clay Neighbor's AAP All Natural" Premium Optimized Custom Fish Food Crumbles).

More information about salt use:
Aquarium Answers, Salt in Freshwater Aquariums

As for the fry, I have achieved phenomenal success by simply powdering Spirulina Flakes at the time of most of my livebearer breeding, of which I had several tanks of Platties alone. I was using Green Flake Plus which is currently not available, but similar products such as Spirulina 20 still are. I also would supplement them with frozen baby brine shrimp or microworms.

The best fish food, Superior to ALL other fish Foods in quality

Fish food Resources:

*Spirulina 20 Fish Food Flake
*Freeze Dried Fish foods; Worms, Brine Shrimp
*"Clay Neighbor's AAP All Natural" Premium Optimized Custom Fish Food Crumbles

Most livebearers of both sexes will eat their young so separation of all other fish is best and the use of a heavily planted aquarium (live or fake) or breeder trap for the female is advised.
Both swords and platties are capable of cross breeding as are Mollies and Guppies.

For further information please read my article about the care of Mollies (of which the care for other livebearers is similar):
Aquarium Answers: Keeping Mollies in an Aquariums


Lake Malawi African Cichlids, female and male Kenyi, photo courtesy Eve In Cichlids some species, males and females are readily distinguishable by color, size or shape.
For others it is difficult or even impossible to tell the sexes apart in non breeding individuals.

Here are a few specific methods to sex certain Cichlids:

Here is a tip as to determining Mbuna African Cichlids from Jon V. (from "Everything Aquatic"):
"When you get a group of fry or brood, keeping them in their own grow out tank for about a month. During this time as you feed fry foods, watch the group to see who's getting the most of the foods. Even at that early age, I've seen a tendency which I think is noted in other forums, that males will even be aggressive for food as early as the first few days when released. After about one month of this, you can take a brood of say about 20, and the ones that have already grown out larger then the others, you have about a 75-80% chance, those are males. While I've seen on some occasions, females grow rather large early on, I find this has great accuracy when comparing the first and second months of age."


See this article from Jon V from Everything Aquatic:
Venting cichlids to determine sex

For more about sexing cichlids (from Ron Coleman’s Cichlid Research Site):
Cichlid Research- Sexing Cichlids


Sexing Goldfish is very difficult before they reach sexual maturity.
One way to tell is by looking at the shape of the vent. Females may have rounder convex vents while males have thinner concave vents.
The pectoral fins of males may be rather thick and stiff (compared to those of female goldfish) and with a more pronounced outer ray.

Another way to tell is by male goldfish will developing breeding stars on their gill covers and along the first ray of their pectoral fins when they are ready to breed.

For more about sexing goldfish:
“Goldfish Basics”


Breeding bettas embrace, BC Aquatics Male Bettas in the wild are short finned, so fins are not as reliable a way to tell the sex in bettas and is common belief.

Here are a few ways to improve the accuracy of sexing your betta:

  1. While looking at the male betta head on, there is an extra flap of skin under his body. The extra skin is an extended flap of skin from the gills.

  2. Again look head on, the males will have a much bolder head and fin structure.

  3. While a little less accurate, a male will generally not have a white dot under his body, in between his ventricles. Females will have this white dot.

Taken together you can give a much more accurate assessment of your Bettas sex.

See this article for more about Betta Habitat of which this knowledge may help in stimulating Betta Breeding behavior:
Betta Wild Habitat


Cousins to the Betta, in which both have a labryinth organ, which allows them to breath air directly. Both also come from SE Asia.

Many Males can be differentiated from females by the shape of the dorsal fin, which is long and pointed in males, compared to the females' shorter and more rounded dorsal fin.
Females that are prepared for spawning will show a pronounced swelling in the breast area, while the male will be more slender in the breast area.

In many Dwarf Gouramis, the males are much more colorful than the females (this is not usually true from my experience with other Gouramis such as blues).
Please note that these are generalizations and do not apply to all Gouramis.

Gourami sexing, male, female, dwarf

Currently I have not found any in depth articles about Gouramis (other than species specific) that I can recommend.
Either I will write one at some point in the future (as I did for mollies) or if one is brought to my attention, I will post it.

Other Recommended Reference Sites

Aquarium Information
Aquarium and Pond Information
-A useful source for current

Aquarium Lighting
Aquarium Lighting; Basic to Advanced

*Filtration Aquarium Filter Help, Troubleshooting, Reviews

*Best Aquarium UV Sterilizer Information
UV Sterilization for Aquarium or Pond

A MUST READ article for anyone looking to move up from basic to more advanced fish keeping!!

*Ick; Ichthyophthirius Multifilis, Treatment, Identification, and Life Cycle

Fish as Pets Aquarium NewsFISH AS PETS
Fish as Pets with articles & commentary of Interest to the Aquarium Hobby
Including articles such as this one:
Melafix Dangers; Effect of Water Parameters on Melafix when used for Bettas, Labyrinth Fish

Aquarium Power Head PumpSunSun JP-023 Aquarium Power Head Water Pumps

Superior performance and value when compared to many more well known brands such as Hagen or Marineland

Fluidized Aquarium Filter
TMC Premium Fluidized Sand Bed Filters

Premium, second to NONE Aquarium Bio Filters, that with optional Oolitic Sand also maintain essential marine aquarium calcium levels, alkalinity, & electrolytes that are important to ALL Marine life, Goldfish, African Cichlids, Livebearers & more


Labels: , , , , , ,

<< Home

This page is powered by Blogger. Isn't yours?

Article Research Sponsor
Remember, it is your purchases (both small & large) at our primary sponsor, AAP, that keeps these world class information articles free.
Or please consider a donation (especially International users of this information), even just $5 usd helps.
As our primary sponsor is AAP, which provides little income for its owner after paying staff (including to help others) & upkeep of this information!

If only 10% of users of this information donated $5, this information will be able to remain free in the future!


In Chronological order of writing with the newest at the top

  1. How to Treat Sick Fish
  2. Whirling Disease in Fish
  3. Reef Aquarium Chemistry Maintenance
  4. Use of RO, DI, Softwater in Aquariums
  5. Lighting Theory of a Planted Aquarium- RQE, PFY, PAS, & PUR
  6. Aquarium or Pond Bio Load
  7. Tuberculosis in Fish
  8. PUR vs PAR in Aquarium Lighting
  9. Head Pressure in Aquarium and Pond Water Pumps
  10. Fin/Tail Rot For Betta & ALL Fish
  11. Angelfish Virus/Aids
  12. Activated Carbon
  13. Fish Baths/Dips as an aid to treatment
  14. Streptococcus gram positive bacterium in aquariums, Eye Infections
  15. Hydrogen Sulfide
    production in anaerobic De-Nitrification for Aquarium/Ponds
  16. Fish Shipping
  17. Aquarium Size, Fish Stunting
  18. Aquarium Algae,
    BBA & Brown Algae in particular
  19. Aquarium Salt (Sodium chloride) in Freshwater Aquariums
  20. Betta Habitat; Wild Bettas to Domestic Betta environment parameters
  21. HITH; Hole in the Head Disease
  22. Aquarium Protein Skimmers, Ozonizers
  23. Power Head/ Water Pump Review
  24. Molly Disease/ Mollies in an Aquarium
  25. Basic Fish Anatomy, Fin Identification
  26. Aquarium Moving/ Power Failures
  27. Octopus as Aquarium Pets
  28. Aquarium Nitrates
  29. Ichthyophonus protists, fungus in fish
  30. Aquarium and Pond Filter Media
    Types; Mechanical, Bio, Chemical
  31. Aquarium Water Conditioners (also Pond)
  32. Fish Parasites; Trematodes & Monogeneans; Annelids and Nematodes;
    Flukes, internal worms, Detritus Worms (often confused with Planaria), Micro Worms
  33. Aquarium Silicone Application;
    DIY Aquarium Repair & Glass thickness
  34. Pond Veggie Filters; DIY Bog Filter
  35. The difference between Plaster of Paris and Aquarium Products such a Wonder Shells:
    Identification, prevention & Treatment
  37. AQUARIUM TEST KITS; Use & Importance
  38. SEXING FISH; Basics
  39. Chocolate Chip, Knobby and Fromia Starfish
  40. Freshwater Velvet & Costia
  41. Usnic Acid as a Fish Remedy
  42. Aquarium Heaters; Types, information
  43. The Lateral Line in Fish, Lateral Line Disease
    or Head and Lateral Line Erosion (HLLE)
  44. Tap Water use in Aquarium; Chloramines, Chlorine
  45. Can Black Ghost Knife fish give an electric shock?
  46. Bio Wheel Review; Do Bio-Wheels really work?
  47. How do Fish Drink?
    Use of RO Water
  48. Cyclops, and Predatory Damselfly larvae
  49. Betta with Dropsy;
    Treatment and Prevention of DROPSY in all fish
  50. pH and KH problems in African Cichlid Aquarium
  51. Aquarium Gravel, which size?
  52. Blue green algae, Cyanobacteria in Ponds/Aquariums

If you have found this site helpful (or the sister site Aquarium and Pond Information),
please consider adding a link to one of our articles from your own blog or website.

American Aquarium Products along with "Aquarium/Pond Answers" (& other information sites AAP has made or purchased such as Fish Beginner), and our VAST library of information found NOWHERE else, in the world is currently FOR SALE for the right offer. As well our inventory is also part of the offer (currently as of 2021 valued at about $44,000 wholesale).
We hope to carry forward our company's 40+ year legacy of unique information (this also includes several other web and blog sites as well).

Only serious inquiries of at least $50,000 for everything (including inventory) from qualified potential buyers will be considered

Recommended Related Information Sites & Products from our family of PROFESSIONAL aquarium and pond websites:

For help with your Aquarium Chemistry:
Aquarium Chemistry; In Depth Information

World Class Aquarium Information
For unique aquatic products (most professionally tested) and information;
*American Aquarium

Free Shipping AAP

*Sponge Filters that far outperform all other brands or DIY:
*Patented Lustar Hydro Sponge Aquarium Filters

UV Replacement Bulbs/Lamps Directory:
*UV Bulbs directory

*A CLEAR POND; Care & Information

Fish Food Information:

Aquarium & Pond UV Sterilizer Use Articles
-Unique articles such as unique UV ideas as well as dispelling myths

Directions/ Instructions/Downloads; Aquarium Pond Products

Aqua UV versus TMC UV Sterilizer
VIDEO: Aqua Pond UV vs TMC AAP Pond UV Clarifier Sterilizer

A comparison of the two top large pond/aquarium-system UV Sterilizers and why the AAP/TMC comes out as the best when price and dwell time is considered

Best Aquarium & Pond Medications
VIDEO: AAP Professional Aquarium & Pond Medications


#Best Aquarium & Pond Fish Products, Grants Pass Oregon

#eBay Community Forum & Bullying, Customer Service

For Website Building/Hosting and who Aquarium Answers recommends (& uses for sister websites):
Website Hosting, powerful web site maker, ecommerce
Make a Website on

All articles are the copyrighted material of Carl Strohmeyer, these can be used ONLY in part and only with proper hyper link.
Use with Google Adwords/Adsense is STRICTLY prohibited without revenue sharing

FishLink Central

#Great Links
#Carl Strohmeyer; Biography
#Ocean Decor


For ALL questions, please refer these questions to:
Everything Aquatic Professional Forum Board