Feeding empire gudgeon (Hypseleotris compressa) fry...

LordJoshaeus · Oct 8, 2019

Hi everyone! Another question regarding breeding an animal not typically thought of in the context of breeding marine fishes...the empire gudgeon, Hypseleotris compressa. The adults are tolerant of full strength seawater but typically live in freshwater in the wild; they are beautiful, peaceful, not too big, not picky eaters, hardy, they don't even need a heater in the average home...BUT there's a catch; they are notoriously challenging to breed. Their eggs are the smallest eggs produced by any vertebrate (a mere 320 microns tops!) and the newly hatched fry (which, in the wild, drift downstream to estuaries and require brackish or marine conditions to grow) are no bigger at 1mm at hatching. Even freshwater infusoria is not small enough to be accepted by these tiny fry.

Now, here's my question; what on earth could possibly be small enough to feed these tiny fry? Obviously something must exist...after all, they wouldn't exist otherwise and I have read of at least one report (here; https://www.aquagreen.com.au/plant_data/Hypseleotris_compressa.html) of them being successfully (ableit accidentally) raised to a size where they will take normal foods. I would really love to take a shot at raising these, as captive bred empire gudgeons would likely be even hardier than the typical wild caught specimens. Thanks

HotManwich · Oct 10, 2019

I'm going to make an educated guess and say phytoplankton might be the best foods for something that small. They also might graze on bacterial films and other microorganisms that are small enough for rotifers to eat. I'm going with rotifers as a size reference because it sounds like some species might be about the same size as your fry.

Mind, I'm not an expert but it seems likely for that stuff.

sabeypets · Oct 13, 2019

"Parvocalanus crassirostris is a small, pelagic calanoid copepod. The nauplii (larval stage) are small, measuring in the 50-100 µm range, making them a suitable feed for small-gape larval fish." this is a quote from Reef Nutrition. There are also a couple of other copepods that are being used.

LordJoshaeus · Oct 13, 2019

sabeypets said:
"Parvocalanus crassirostris is a small, pelagic calanoid copepod. The nauplii (larval stage) are small, measuring in the 50-100 µm range, making them a suitable feed for small-gape larval fish." this is a quote from Reef Nutrition. There are also a couple of other copepods that are being used.

True...but these fry cannot even swallow freshwater infusoria, so I am not sure even copepod nauplii would be small enough initially. Thanks, though

Reef Nutrition · Oct 14, 2019

LordJoshaeus said:
Hi everyone! Another question regarding breeding an animal not typically thought of in the context of breeding marine fishes...the empire gudgeon, Hypseleotris compressa. The adults are tolerant of full strength seawater but typically live in freshwater in the wild; they are beautiful, peaceful, not too big, not picky eaters, hardy, they don't even need a heater in the average home...BUT there's a catch; they are notoriously challenging to breed. Their eggs are the smallest eggs produced by any vertebrate (a mere 320 microns tops!) and the newly hatched fry (which, in the wild, drift downstream to estuaries and require brackish or marine conditions to grow) are no bigger at 1mm at hatching. Even freshwater infusoria is not small enough to be accepted by these tiny fry.

Now, here's my question; what on earth could possibly be small enough to feed these tiny fry? Obviously something must exist...after all, they wouldn't exist otherwise and I have read of at least one report (here; https://www.aquagreen.com.au/plant_data/Hypseleotris_compressa.html) of them being successfully (ableit accidentally) raised to a size where they will take normal foods. I would really love to take a shot at raising these, as captive bred empire gudgeons would likely be even hardier than the typical wild caught specimens. Thanks

There are plenty of motile algae that they are probably eating. Larval marine fish do this. Tetraselmis sp. is a good one. This marine microalgal species is only about 15 microns and swims rapidly through the water column. There are also plenty of ciliates in the 20-30 micron ranges, like Euplotes sp. Infusoria is supposed to contain a lot of these things, so not sure why that isn't working.