60 Gallon Tank Rainbowfish behaving strangely (emergency?)

Tank
What is the water volume of the tank? 60g
How long has the tank been running? Over a year
Does it have a filter? Yes
Does it have a heater? Yes
What is the water temperature? 76F
What is the entire stocking of this tank? 3 garas, 3 flying foxes, 3 yo-yo loaches, 3 dwarf rainbowfish, 3 bosemani rainbowfish, a few ramshorn snails
(Please list all fish and inverts.)

Maintenance
How often do you change the water? Once every two-three weeks
How much of the water do you change? 25-30% on average
What do you use to treat your water? Nothing
Do you vacuum the substrate or just the water? Just water

*Parameters - Very Important
Did you cycle your tank before adding fish? Yes
What do you use to test the water? API test kit
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0
Nitrite: Did not have enough solution to test
Nitrate: See Nitrite
pH: 8.4

Feeding
How often do you feed your fish? Once a day
How much do you feed your fish? 4-5 pinches of flakes for rainbows, 6 carnivore sinking pellets and two algae tabs for rest.
What brand of food do you feed your fish? Aqueon tropical for rainbows
Do you feed frozen or freeze-dried foods?
No
Illness & Symptoms
How long have you had this fish? Bosemani’s just over a week, Dwarfs about three months
How long ago did you first notice these symptoms? Less than an hour ago.
In a few words, can you explain the symptoms?
Swimming at the surface, almost look to be gasping but not as bad as I have seen for ammonia symptoms. Did not see if they ate but the food was gone. The three Bosemanis and two of the three dwarf rainbows are doing this, the largest dwarf rainbow is behaving normal

Have you started any treatment for the illness?
No because I do not know the issue.

Was your fish physically ill or injured upon purchase?
No
How has its behavior and appearance changed, if at all?
Appearance is the same as usual, behavior is described above.
Explain your emergency situation in detail.

Since it looked like ammonia symptoms I checked that immediately with the API test kit and the reading came out as 0.0. Tested it again to be sure and got same results. Tested PH as well for this post but do not have enough Nitrite or Nitrate test to run it as I used them up from biweekly tests. The dwarf rainbows have been fine for three months and I only just noticed this today, hadn’t seen any issue with the bosemanis before this point, they had acclimated nicely. Is this normal/ok behavior, or a symptom of something wrong with the water? Could it possibly be Nitrate or Nitrite? I did a 25% water change last week. Anything helps. Hopefully everything’s still alive and well in the morning, will update.
To add, the fish in question are pretty active still, I wouldn’t describe them as listless or anything like that. Also all the other fish breeds are acting like normal.

 

Reading your notes, the maintenance schedule is not ideal for that level of stock. Weekly water changes of 50% will take care of any issues on the chemistry side. You say that you do not treat the water when water changing, is there a specific reason such as well water or non chlorinated water etc?

The latest fish to be added, did you quarantine before adding to the aquarium as the reason for the issues you describe could be a health issue introduced by the new fish. Illness and disease does not show up immediately, it can take a couple days to a month or more to establish itself in an aquarium and for fish to show symptoms or distress.

I strongly suggest that you buy replacement testing fluids asap so that you can run a more accurate test on the chemistry.

 

The only ones at the top are the rainbows? Are they chasing each other? What type of filtration. 50% water change weekly is needed to keep rainbows healthy. Next a temp of 78-79 is what mine enjoy. Now 7yrs old.

 

You say that you do not treat the water when water changing, is there a specific reason such as well water or non chlorinated water etc?

It is well water.

The latest fish to be added, did you quarantine before adding to the aquarium as the reason for the issues you describe could be a health issue introduced by the new fish. Illness and disease does not show up immediately, it can take a couple days to a month or more to establish itself in an aquarium and for fish to show symptoms or distress.
I strongly suggest that you buy replacement testing fluids asap so that you can run a more accurate test on the chemistry.

I couldn’t quarantine them because I don’t have space for a quarantine tank.

I plan to.

 

It is possible that the latest arrivals did bring something with them and without quarantining them, which I completely understand since not everyone has the room for a spare aquarium that gets used infrequently.

Once you have your new test kit, you might also test the well water before putting it into the aquarium, just to check for any leeched residues in the water that could upset the chemistry....you probably would not notice it but the fish almost certainly would and behave differently as a result.

Once you have the new test kit and increase the water changes to weekly / 50%, you may well see an improvement generally across all of your fish. Try to resist reaching for the medications, just keep the water clean and fresh with a rigid water change routine...and test the water before it goes into the aquarium before water changes for peace of mind.