Baby Fish Magically Appeared

[Dr. Fish-Leg]

Hey awesome folks of reef2reef,

I have a macro-algae dominant aquarium in a Fluval Evo 13.5 (see video below). I only had 2 fish - a Yellow Stripe Goby and a juvenile Chromis - in the tank (along with some inverts) until yesterday, when I introduced a Hector's Goby and a Tail Spot Blenny to consume some micro-algae that's thriving a bit too well for my liking lol. The "pack" works well and I really enjoy watching their interactions.

Today, as I stopped the return pump to add some pellets and zooplankton, I noticed that, among the "root system" of my Caulerpa Prolifera and behind the Mermaid's Fan, there were two cute baby fish feeding and swimming about (see videos below). It's such an amazing surprise but it does make me very curious: where the hell did they come from?

As I only have a single fish per species, I'm inclined to believe that they must come from a live-bearing mother fish that was one of the 4 fish I have. Does anyone know what baby fries look like for these 4 species? I am a fish geneticist from New Zealand but I'm not well versed in the morphology of juvenile fish haha. Another possibility is that these 2 cuties came from hatched eggs attached to macro-algae or some rocks but since baby fish usually have a pelagic phase floating around in the water column, they would have been "washed down the drain" and caught in the floss way before growing to this size. I wonder if anyone else had a similar experience or an interest theory to propose. There is never a dull day in the aquarium hobby!!

Thanks for your time in advance!

Cheers
Jack

 

[Jay Hemdal]

I can't tell you what species the baby fish are, but they are not offspring of the fish you have in your tank. All of those are egglayers with pelagic larval stages.

Those fish are either a Poecilid (livebearer) or a Cyprinodontiforme (killifish and their relatives). I'd vote for the latter - I've had killifish show up in tank where the eggs were transported there on plants or algae. The baby killifish are mobile enough not to all be sucked into the filtration system, and a few may find enough to eat from the microfauna in the tank.

Jay

 

[WheatToast]

Those fish are either a Poecilid (livebearer) or a Cyprinodontiforme (killifish and their relatives). I'd vote for the latter - I've had killifish show up in tank where the eggs were transported there on plants or algae. The baby killifish are mobile enough not to all be sucked into the filtration system, and a few may find enough to eat from the microfauna in the tank.

+1. My LFS has had rainwater Killifish (Lucania parva) appear in their refugiums before. I accidentally saw them in-person long before finding this Reef Central post, while watching them harvest Chaetomorpha from their sumps:
http://www.reefcentral.com/forums/showthread.php?t=2699134

Other instances of killifish hitchhiking into tanks:
https://www.reef2reef.com/threads/mystery-fish-in-my-invert-qt-tank.400132/
https://www.reef2reef.com/threads/bully-fish-help.918488/
https://www.reef2reef.com/threads/hitchhiker-fish.746979/
https://www.reef2reef.com/threads/hitchhiker-fish.460055/

 

[Dr. Fish-Leg]

I can't tell you what species the baby fish are, but they are not offspring of the fish you have in your tank. All of those are egglayers with pelagic larval stages.

Those fish are either a Poecilid (livebearer) or a Cyprinodontiforme (killifish and their relatives). I'd vote for the latter - I've had killifish show up in tank where the eggs were transported there on plants or algae. The baby killifish are mobile enough not to all be sucked into the filtration system, and a few may find enough to eat from the microfauna in the tank.

Jay

Thank you so much for the insightful reply Jay! It's great to confirm that none of the 4 marine fish I have are livebearers and therefore not possible to have given birth to the 2 babies. And thank you for the suggestions. I managed to capture another video of them and they do look like killifish of some sort and most of my algae was collected in the wild in Florida so it all makes sense now! Thank you so much for solving the mystery!!

 

[Dr. Fish-Leg]

+1. My LFS has had rainwater Killifish (Lucania parva) appear in their refugiums before. I accidentally saw them in-person long before finding this Reef Central post, while watching them harvest Chaetomorpha from their sumps:
http://www.reefcentral.com/forums/showthread.php?t=2699134

Other instances of killifish hitchhiking into tanks:
https://www.reef2reef.com/threads/mystery-fish-in-my-invert-qt-tank.400132/
https://www.reef2reef.com/threads/bully-fish-help.918488/
https://www.reef2reef.com/threads/hitchhiker-fish.746979/
https://www.reef2reef.com/threads/hitchhiker-fish.460055/

Hey WheatToast! Thanks so much for sharing your story and the related posts! They are super helpful! I never thought that killifishes are capable of living in full saltwater but it looks like they do it on a regular basis! This is so incredibly fascinating! I could hardly believe my eyes when I saw the 2 small fish the other day. This is like having freshwater fish without setting up a freshwater tank lol.

Cheers
Jack