Sick Oranda

Question
Hi good day,

I have a 38L tank, with filter system (Jebo make). I have a few Java Ferns in the tank that I got from my brother since he didn't like the look of them in his tank and I love them again. Also have a bit of a floating plant (cant remember the name but its spindly and the goldies love it , my LPS was surprised to see i buy it as a snack for the goldies and they seem to thrive on it as well as the Tetra goldfish granules.

I noticed that a day ago my two oranda's started sitting at the bottom of the tank, then have a mad dash swimming around the tank just to settle at the bottom again. Both of their fins are showing red streaks and the one is clamping his fins to his body. The one clamping his fins to his body is also bloated, but only on one side of his body.  

I figured he was constipated and gave them a couple of mushed peas without the skins - they adore that btw, its a weekly treat in any case.

This morning he is sitting in a corner hiding almost, definitely not feeling well.

Oh and the tank water was tested on yesterday and was told the parameters are fine.

Strangely enough my other two calico goldies are fine and very
active. (I have all 4 in the tank - do weekly 25% water changes and gravel vac their tank once every 3 weeks.)

Answer
Your fish is dying of ammonia and nitrite poisoning.

The cleaning isn't enough.  You need to increase it.  A 38L tank is a tank that is only about 7 gallons US.

That means that the fish is way too cramped.  The rule of thumb is 1 baby goldfish per 10 gallons and 1 adult goldfish per 25 to 50 gallons.  They are extremely filthy fish and they cause the water quality to get very filthy very fast.  25% water changes are sub-standard.  They need 50% every week and gravel vacuuming.  Can you try to accommodate him with this?  If so, you will probably see a quick turnaround in his health.

The clamped fins of red are ammonia and nitrite poisoning as is laying on the bottom.  His swim bladder has stopped functioning.  That is because the water is filthy.

Clean all filtration media and wash out your filter every week too.  But, today, do a 50% water change, or take the tank apart and thoroughly clean it.

He will improve fast! Just needs clean water. :)

As for testing water, the parameters are not fine.  I disagree...your fish is exhibiting very typical poisoning signs.  Nitrate should be 0 ppm.  Nitrite should be 0 ppm.  Ammonia should be 0 ppm.  Test strips say some levels are safe.  They are not safe.  Indeed, they should show only the lowest level across or a goldfish will suffer.  

Trust me on this please.  I get this question every day.  Water changes...he will improve.

Happy fish-keeping and I will cross fingers for his quick recovery so he can be your best friend again. :)