Sudden Fish Death

Hello everyone! I'm new to marine aquarium. My fish suddenly die overnight after 1 week after my cycling process.



http://ift.tt/1nVcPFk





I need advice from you the experts and the regular to tell me what i've done wrong and what to be aware of!



The parameter of my tank now are

No3 : 40

No2 : 0.5

Ammoia : Safety <0.02pm (Read from Seachem Ammonia Tester)

PH : 8

Kh: 180

GH : 180

Salinity : 1.020-22 Using hydrometer and specific gravity

Temperature: 26degree.





Livestock in the tank.

2 Gold head Sleeper (6cm) Both Dead

1 Blue Tang (7CM) Struggling to survive.

2 Mandarin goby (3CM) (dead)

2 Damselfish (2CM) (1 Alive)

1 Firefish goby ( doing **** well for some reason)



3 coral in tank. All alive.



Two Live rock in tank.



Fine sand ( Not live sand)



The chemicals i use for my tank are.

Continuum Reef•Sculpture parts A and B

Continuum Reef•Basis iodine

Bio bio nitrifying bacteria



Filter

Protein Skimmer Dymax

Nitrate sponge filter

Ammonia sponge filter

3 -in 1 ( Carbon , Bio ball , sponge)



Is there a reason for the sudden cause of death?

The salter i get which are from the shop and the PH are 7.5

Please advice and help!



It take 3 week for my cycle.