How do I get my Co­rys breed­ing?

Practical Fishkeeping (UK) - - Advice -

I have been at­tempt­ing to breed my

Co­ry­do­ras pyg­maeus for around six weeks. I have five left af­ter my group of 10 was re­duced by a bac­te­rial in­fec­tion, and I wish to bring their num­bers back up the ‘nat­u­ral’ way.

I def­i­nitely have a mix of male and fe­male. How­ever, my ob­ser­va­tions as to how many of each swings back and forth de­pend­ing on how much live food I’ve been giv­ing them!

They are cur­rently in a 25 l/5.5 gal tank with a sponge fil­ter, two or­na­ments for hid­ing, and a thin layer of sand. My method is to do daily 50% wa­ter changes, top­ping the tank back up with a mix of 50% RO wa­ter and 50% tap­wa­ter (which has a ph of around 7.5). But I’m get­ting no breed­ing be­hav­iour at all and can only find con­flict­ing opin­ions and ad­vice on­line and at my lo­cal fish shop. What is your take on this?

Also, should my Co­rys breed, will pond snails, Malaysian trum­pet snails or Ramshorn snails eat the eggs? ANDY, EMAIL

BOB MEHEN says: Pygmy co­rys are lovely lit­tle fish. Due to their small size and pop­u­lar­ity they make a great breed­ing project and it’s easy to find new homes for any ex­tra young­sters. It sounds as though most of what you have done so far is a step in the right di­rec­tion, and with a few small changes you may have more suc­cess.

What is the ph of the wa­ter in your tank? The ph of 7.5 you men­tion is prob­a­bly a lit­tle high, es­pe­cially if you’re in a hard wa­ter area. Ide­ally you want soft, slightly acidic wa­ter with a ph of around 6.5. This might not sound like a big dif­fer­ence but the ph scale is log­a­rith­mic, so ph 6.5 is 10 times more acidic than ph 7.5. Like many Co­ry­do­ras, it seems that

C. pyg­maeus spawns af­ter rain­fall in the wild, so drop­ping the tem­per­a­ture of the wa­ter you use for your wa­ter change by a few de­grees from that in the tank, and in­creas­ing cir­cu­la­tion (per­haps adding an ex­tra air­stone) may help sim­u­late this and trig­ger spawn­ing. You also need to make sure you con­di­tion the fish well be­fore­hand with a good se­lec­tion of ap­pro­pri­ately sized foods. Frozen foods like Daph­nia and Cy­clops help in my ex­pe­ri­ence. Hav­ing more males than fe­males is good too, as the ex­tra com­pe­ti­tion stim­u­lates them fur­ther.

Most Co­ry­do­ras will eat their own eggs so it’s best to re­move the par­ents af­ter spawn­ing – this will also make it eas­ier for you to pro­vide the best con­di­tions for the fry to thrive, as well as re­move com­pe­ti­tion for food.

I wouldn’t trust snails with the eggs ei­ther, so make sure there are none in the breed­ing tank.

Cool acidic wa­ter is whats needed for cory breed­ing.

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