Hello! I have a 30 gallon planted aquarium with 8 harlequin rasboras (two died last night), 6 bronze cory cats, and 2 nerite snails. The tank was cycled for 2 months before adding fish, and i have added fish slowly over the past ~6 weeks. I do 30% water changes every week and test the water twice a week.
Current specs: 76°F, pH: 7.2, Ammonia: 0.25ppm, Nitrite: 0ppm, Nitrate: 20ppm. I have a Fluval 50 AquaClear HOB
filter and an air pump.
4 days ago, the Ammonia was 0 and the Nitrate was 5ppm. I just did an 80% water change, rinsed my filter materials in tank water, scrubbed algae off my driftwood, and wiped down the glass. I suspect the Ammonia is what killed my two fish.
All of my other fish appear to be fine - full of color, swimming, eating. The two dead rasboras had lost all color and were the youngest of the school. One was bloated near the filter and the other was shrunken, sunk to the bottom of the tank. These two fish must have died some time in the night, as I fed them and did a count before going to bed.
My problems: I don't know where this ammonia spike came from (could be from over feeding, but I'm pretty good at cleaning whatever they don't eat). There are many particles in the water and the water is more brown than it was ~4 days ago. Many of my plants (Pennywort, Lloydiella, Hornwort) are turning brown and being covered with brown algae. I can rub the brown spots off the stem plants, but not the Hornwort.
So, I'm not sure what I should do next... I've limited the photoperiod to 6 hours and rinsed off most plants. Should I buy something to eat this brown algae?? Some shrimp?