To summarise the answers so far:
2~What are your tank parameters (ammonia, nitrites, nitrates, temp, pH)? Please give exact values. ______ Temperature somewhere between 20 C to 28 C.
3~ How large is the tank? 60 liters = 15.5 gallons How long has the tank been set up? 8 Months?
4~What type of filtration are you using? ___________ Please give the name and number (i.e. Fluval 304) and amount of gph if known. ____________
5~How many fish are in the tank? __________ What kinds of fish are they and what are their current sizes?
fish:
1 betta (now dead)
1 opaline gourami Current size?_____
1 yellow lab Current size? _____
1 gold fish which has become white Current size? ____
1 Oscar Current size? ______
1 Unknown fish? (irridescent shark?) Current size? ______
6~When is the last time you did a water change and vacuum the gravel?_______? How often do you do this? _________? How much water do you remove at a time? __________?
7~How long have you had the fish? 8 months? If the fish is new, how did you acclimate it/them?
8~Have you added anything new to the tank such as decor, new dechlorinator, new substrate, etc.?
9~What kind of food have you been feeding your fish? have you changed their diet recently?