A disheartening start with O. latipes -- advice appreciated

[I Like Plants]

Hello all! 

I'm having a bit of trouble with a batch of Japanese rice fish/medaka/Oryzias latipes, and I was wondering if anyone out there who's more knowledgeable than myself could give me a hand. I took a break from fishkeeping after moving cross country, and this is a bit of a disheartening foray back into the hobby. 

Parameters:

• 20 gal tank, about a year old, other occupants are 15+ RCS and a handful of snails, pretty well planted
• pH 7.2, ammonia 0, nitrites 0, nitrates <5ppm
• Water temp is 76F

The situation:

• Ordered a group of 8 "blue sparkle" medaka. Shipment arrived on time, but the bag was leaking and HOT when it arrived. The fish were shipped in a styrofoam container, but the interior was really warm. Still, all 8 fish were alive and active. One fish was missing an eye, but it didn't appear to be a new injury.
• Day 1: Drip acclimated the fish, kept them in a breeder net for 24hr to observe. They all seemed active, alert, and acclimating well. All of the fish were eating and swimming well through the end of Day 2. Tested water levels and did a small water change in the afternoon of Day 2.
• Day 3: One of the smallest fish seemed to be breathing quickly/swimming near the surface at the end of Day 2. It declined quickly overnight and was dead on the morning of Day 3. The next smallest fish followed a similar trajectory and was dead by the end of Day 3.
• Day 4: The largest fish, a female, got stuck in some algae near the back of the tank. I've had a bit of a hair algae problem in the past. Things have been much better, but I guess I missed a clump in the back. I gave the algae a bit of a nudge and she quickly swam free, but she's been hyperventilating ever since. She hasn't been eating, has been swimming near the surface, but also has bursts of energy where she swims around the tank. At the end of the day, I noticed a small red splotch on her back. The remaining 5 fish seem to be doing fine and are eating and swimming well. Tested water levels and did a small water change.
• Day 5: Today. Big girl seems to be struggling even more, the red splotch is bigger, and she's drifting nose-up. I gently scooped her into a breeder net (with some plants for cover) for closer observation. One of the other fish is still swimming normally, but he seems to have popeye in one of his eyes. Another fish is swimming near the top of the tank like the others were before they died. Three appear to be doing okay.

What am I doing wrong here? Aside from ordering fish during the summer (which, really, I should've thought of beforehand), I can't pinpoint what's going wrong. Is it a delayed reaction to the shipping/acclimation? Am I missing something?

 

Any input y'all have would be much appreciated, and I'm here to answer any questions.

Thanks!

--Plants, a frustrated fishkeeper

[Colu]

Frist I would add an extra air stone heavy breathing near the surface could be low levels of desolved oxygen popeye caused by a bacterial infection I would treat with maracyn and aquarium salt 1 table spoon for 2 the salt will help reduce the fluid buildup in the eye if you have live plant salt at that level will harm them you can do a salt bath in a bucket 1 table spoon for 2 gallons for no more than 15 minutes 2-3time a day

[I Like Plants]

On 7/19/2021 at 10:15 AM, Colu said:

Frist I would add an extra air stone heavy breathing near the surface could be low levels of desolved oxygen popeye caused by a bacterial infection I would treat with maracyn and aquarium salt 1 table spoon for 2 the salt will help reduce the fluid buildup in the eye if you have live plant salt at that level will harm them you can do a salt bath in a bucket 1 table spoon for 2 gallons for no more than 15 minutes 2-3time a day

Thanks Colu! I appreciate your input. Low oxygen levels were something I'd considered. My tank has a spray bar, and I adjusted it to create more surface agitation when I noticed the heavy breathing. Still, I'll add another air stone to see if that helps.

The aquarium salt bath seems like a reasonable course of action. I'll pick up some aquarium salt and maracyn after work today. I'm a bit worried about stressing them out more by moving them to a bucket/giving them a salt bath, but it might be the best way to go.

 

Fingers crossed! I'm hoping to avoid more casualties. We'll see how it plays out.

 

Thanks again!

 

[T. Payne]

It certainly is possible that the fish are still struggling because of the poor condition they arrived in from shipping.  In my experience, they are one of the hardier fish I keep. I have kept and bred them both inside/outside, in lower ph and softer water and with a ph of 8 and rock hard water.