New tank, early loss of Phoenix Rasbora fish

Hi, I set up a 10l nanotank at Christmas and it finished cycling on Thursday 23rd Jan. It has soil substrate, dragon stone, java moss, java fern and dwarf grass. On Friday 24th I completed am 80% water change and bought 6 phoenix rasborah fish. All was well on Friday and Saturday. I was missing a fish Sunday night as in I couldn't find it and on Monday morning 2 fish died without any strange behaviour. I tested the water and had zero ammonia and nitrite but approx 40 to 60 ppm nitrate. I immediately did a 70% water change dechlorinating the water and 1 of the 4 fish looked sluggish. Sure enough this morning it was dead. So that's 3 fish dead in 4 days. I feed them flake once a day that I ground into a powder. Any advice on what could have happened?

 

Consieering your water parameters are fine and you properly cycled the tank, my guess is a disease, possibly columnaris.

 

I would say it could be the nitrates and the PH being high. What is yours PH. These fish are rather sensitive to water quality. Could very well be disease.
How did you acclimate them? The LFS might be running lower ph and you may have shocked them.

Phoenix Rasbora (Boraras merah) - Aquatic Arts

 

Hi, thank you for the reply, I acclimatised them by floating them for approx 45 mins and then straight in the tank. pH is currently 7.2 but does usually settle at 6.8, nitrates at 5 ppm after yesterday's water change. PH in the store was 7.4.

 

Hi, thank you for the reply, I acclimatised them by floating them for approx 45 mins and then straight in the tank. pH is currently 7.2 but does usually settle at 6.8, nitrates at 5 ppm after yesterday's water change. PH in the store was 7.4.

I’d say sick from the store or a bad batch.
I bought some runny noses tetras recently and 10 bought ten then added five more. The first ten are great. The second five are dull, don’t school, and seem to breath heavier. Two died and I have 3 left but they never looked good from the start.
Some fish just don’t travel well.