I need help figuring out what is killing my cichlids

[John J Pollock]

Until this morning I had 5 small African cichlids a placosthamus and a small catfish in a ten gallon tank with a water fall style filter. when i went to bed last night everything was fine the water was clear and all the fish where alive. when I woke up this morning (6 hours later) the water was extremely milky (can't see the back of the tank) with some foam on top and all of the cichlids where dead, the other fish seam fine. I checked the ph it's neutral. the tank has been set up for around 8 months. I changed the water and cleaned the gravel 2 weeks ago. I want to figure out what did this before I get new fish so what ever it was can be prevented, any ideas?

 

[Meredith]

Answer these Qs to ensure we have as much information as possible about your ailing fish and its environment:

1~What type of fish is afflicted? In addition, please describe what is wrong with the fish to the best of your ability (i.e. cotton like growth, bloated, etc.).
2~What are your tank parameters (ammonia, nitrites, nitrates, temp, pH)? Please give exact values.
3~ How large is the tank? How long has the tank been set up?
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?
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? If the fish is new, how did you acclimate it/them?
8~Have you added anything new to the tank--decor, new dechlorinator, new substrate, etc.?
9A~What kind of food have you been feeding your fish, have you changed their diet recently?

 

[BrianNY]

Five fish dying in one night definitely points to something environmental. The fish decaying in warm water could account for the cloudiness. Were all of these fish in the tank for eight months? What kind of pleco and catfish?

My first thought is they were killed by the pleco or catfish while sleeping.