Tomoko, At 1" it can be hard to tell the sexes apart, however females rarely have a lot of iridescent head markings. It looks like you have the same problem many people have found with commercially produced A. borellii. The sad truth of the matter is that most A. borellii being sold through commercial sources are males. I suspect that the breeders are spawned at temperature above 82ºF (28º C) and producing mostly males. What females are produced are probably held back for future breeders. If you really want some females your best bet is to buy from hobbyist/breeders. Shipping can make this rather expensive, however. Otherwise I'd suggest buying the smallest specimens in the tank and hoping some will become females. A 75 gallon tank can easily handle several different species of apistos as long as there are a lot of places to hide and build territories. If the tank is properly landscaped, I doubt you would have many problems mixing A. macmasteri, A. cacatuoides or any apisto with your A. borellii. Just remember that a full grown male Mac will be nearly twice the size of full grown A. borellii. Mike Wise Tomoko Schum wrote: > I hope someone can help me determine the sex of > the young A. borelli I purchased about a week > and a half ago. Both fish are about an inch long > and looking very healthy. One of them is much > darker than the other one, but otherwise they > are identical. They both have the iridescent > blue markings on their heads and dark gray > suborbital stripes, lateral bands, vertical bars > and caudal spots. The body color of the darker > one is light greenish tan with bright iridescent > blue specs (its head looks almost purplish on > occasion). The light colored one is light > bluish gray with much lighter head markings and > body speckles. The darker one is more dominant > and sometimes chases the lighter one away from > his small territory. They live in a 75 gallon > tank. I would like to add more Apisto in the > tank. I can get more borelli from LFS to have a > small harem, but LFS or I can not tell their > sex. > LFS has also macmasteri on hand and on a rare > occasion some cacatuoides. (Then again I have > the same sexing problem.) Can I have two > different species share the tank? TIA, Tomoko > SchumMadison, Alabamatomokoschum@earthlink.net ------------------------------------------------------------------------- This is the apistogramma mailing list, email@example.com. For instructions on how to subscribe or unsubscribe or get help, email firstname.lastname@example.org. Search http://altavista.digital.com for "Apistogramma Mailing List Archives"!