I joined this forum newly but I am reading the posts for almost a month and got a lot of help in setting up my new aquarium.
I just finished cycling my new 72 liter (18 gallon) aquarium (finsh-in cycling using Seachem Prime, Seachem stability, Biodigest Prodibio and water changes).
The water parameters are here
pH : 7.2
: 3 - 8 (this is how my test kit shows)
Temp : 25 deg C (77 deg F) (there is a 25W thermostat heater and thermometer, thermometer is in another side of the tank and never seen it going below 25deg. Thermostat is set to 27 deg)
Ammonia : 0
Nitrite : 0
Nitrate : < 5 ppm
I have a mini canister filter 450 L / Hour (acrylic wool, carbon, sponge , ceramic rings and balls)
There is an air pump which generates bubbles.
There are 3 female bettas, 2 dwarf gouramis, 1 sunset gourami, 1 honey gourami, 2 small black neon tetras and 3 mystery snails in the tank.
The problem i am facing is when I add a fish from the store it is very active until the night falls, next day it becomes lethargic and stops in one place of the aquarium. All the existing fishes are doing the same. The 3 female bettas sleep blow the stones always. Sometimes they go up to breathe and return back to the same place back to sleep. In the morning hours before I feed them they are active and very responsive. But just for few hours. If I feed them or not they become lethargic anyway.
Another important thing is when i do water change all of them come near to the water tube as if they really feel good with the new water and stick around it until I finish. Even sometimes they fight to be close to the water tube. After a water change they remain active for 2 - 3 hours and become lethargic again.
I tried with 4 different kinds of food (different company, also with flakes) but the result is always the same. I feed them once a day (morning) average 3 balls per fish. They eat all the food before falling on the gravel.
All the parameters look normal so I can not understand what is going on. Is it the dissolved oxygen ? I never tested it as i have a air pump running 24 hours.
Please someone give some direction. I will be grateful.