Breeding Common Bristlenoses

General notes on pleco breeding -from my experience.By Irene Miller( Irene0100)

It is often asked -”which plecs are the easiest to breed?” or “ I want to breed plecs -where do I start?” Most often the replies centre around Common Bristle nose (Ancistrus sp.) (BNs for short) as being easy and good for the learning curve. To be fair thats where I started although I was not convinced that I should not start with something more exotic, and what's this learning curve anyway?

Well I did the standard thing and got a pair of BNs, and I did learn quite a lot, despite research and thinking I knew it all!. After that I was lucky enough to have breeding gold Strip panaques (LDA01) and now I have L270 Chocolate Zebras and marbled BNs. BUT it is not as easy as some might think, and fish have their own rules, likes and dislikes and no two fish are the same.

So lets start with some basics.
How to get BNs to breed.

First have one pair (do not get a colony -this only works for some fish) or at most one male and two females.





If you have more than one male they will probably fight -badly, and if not they will spend more time watching each other than having any interest in the females. Besides once they get going you will have so many young you will be glad you only have one breeding pair. If you start with quite young BNs because you cant get adults, don't worry they only have to be about a year or so old to breed (unlike some other plecs you may have to keep for quite a few years first).

As long as they have a reasonable sized tank (2ft plus) good filtration, good water, some driftwood, a few stones and a suitable cave they will probably breed when they are ready. They dont have to be in a tank on their own as long they have nothing they will fight with or is bigger than them and could take over the cave. The cave can be PVC pipe with an end blocked off, a slate cave or pottery – or home made such as an upturned flower pot with an entrance in it. I have heard of some using coconut shells with an entrance and stuck on a bit of slate. I gave mine several to choose from and he chose a home-made clay one. Having said that lots of people also ask – “why wont my BNs breed?”. Well after the obvious question of - are they male and female (male has Bristles up his nose and the female doesn't! see pics) there are a number of things to try and help.

1. Add water from another tank that has breeding fish in it – for example, each water change take out 2 buckets of old water and one new and one from another tank.
If you dont have a tank with anything breeding, add some fish in with the BNs that may breed readily (eg some corydoras -I used trilineatus and panda cories, or small guppies). This helps to put helpful hormones in the water.
A local fish shop who I kept supplied with lots of baby Bns, had his own shop for many years, decided he would try and breed some when I stopped supplying. He was surprised it was not as easy as he had assumed and had been advising his customers for years! But then he did not believe me that you should do a water change (approx 20%) every other day and only did his water changes every few weeks!
He gave up in the end and sold the adults!

2. Very regular water changes, I did every other day, with water the same temp as the tank, just to keep water tip top.

3.Have some plants (java fern is good cos they dont eat that), so nitrates are absorbed and water is well oxygenated.

4.Buy a barometer or watch the weather forcasts. When the air pressure starts dropping and a storm is coming – do a large water change -about 50% - with water that is several degrees cooler than the tank, and if possible use soft water with low TDS, such as RO water or rain water (where rain is NOT off a concrete roof or anything leaching chemicals). Also unplug the tank heater for several hours.

5. Repeat the last step every day for several days. Then let tank rest for a few days.

Once they are breeding, as long as water quality is kept good the big water changes are not needed for further broods.

Here are some of the babies ready to leave the cave, with their dad guarding.


One of the 'lessons' I learnt was about the fry – I did not realise they would swim inside the filter housing and my first breeding tank was a 90 litre juwel which has a fixed internal filter, in black. It was very hard to catch the fry and get them out safe because of the dark and the fry are hard to see as they are also dark.
I soon got a new tank with different filtration that was more fry friendly.

Another lesson is not to shine torches into the breeding caves to see if there are any eggs yet - this can upset them a lot and cause them to kick the eggs out or eat them.
I also learnt that having a lot of wood, plus soft water, tended to make the ph drop suddenly when I did not expect it, so I reduced the an mount of wood and added some buffer to the water. Electronic ph meters are really useful.


I hope this will encourage you because its really exciting when you get your first fry!

young growing up fast!