One of my Angels died

I would strongly suggest in getting some test kits, they are one of the most important things to have. You should get a p.h, ammonia, and nitrite testing kits. They are only around $5 each. What are your tank specs?(size, filtration, temp, how long it has been established)
 
Its a 55 Gallon tank, UG Filter and a Sponge Filter(does bio and mechanical), its at 26 Degrees Celcius atm, and its been running for almost a month.

I have a PH kit and its 7 so nuetral.

I will buy an ammonia and nitrite kit next week hopefully. I just got a new fulltime job so I am planning on buying a canistor filter and better lighting.
 
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