What is killing my clownfish?

Jonathan lee · Apr 11, 2023

Okay i have a 20g tank divided in the centre for my clownfish breeding project. New fish seem to be dying for no reason but there definitely is a reason which i dont know yet. Swimming happily at 6pm then dead at 9pm. But then theres others in there which are fine. Same tank same water. The tank is kept outdoors beside my lagoon mangrove pond that houses angels, foxface, pair of clowns, filefish, alot of mollies. This lagoon is doing great. Fish are happy healthy begging for food when they see me like puppies. But the tank right beside it isn’t. Honestly I’ve killed 3 clownfish now in that tank and i cant figure out whats wrong. The clowns were WC big ‘girls’ 3 inches long minimum and some CB 1.5 inch ones. They all die under 3 days except the first ones i got 2 months ago those guys are ok. I feed 3 times a day and the older clowns eat but the big wc ones dont which is normal fresh off the boat. They are not thin so im sure its not the cause of death since its only been like 2-3 days in there before dying. One difference i found was that the lagoons temp is lower than the tank. Im guessing cause its right up close to a cement wall and cement is cooler. Tank is not surrounded by any walls. I just ordered a cooling fan for the tank to drop temp by 5-6F thinking the temp is the reason the fish die since coming from a cool ocean to my tank with warmer water is a big shock. The fish are caught locally and probably in the store for a week or less before i got them and water temp is 79-80F in the store. Im in malaysia so its hot outside. My reef tank indoors needs a chiller. The lagoon outside is fish only with mushrooms so i didnt hook up my other spare chiller but its doing good.

The fish that die do have weird behavior. Erratic swimming like they just got hit on the head. Even on the way back from the lfs the fish were jumping in the bag splashing alot. Not sure if it has anything to do with their death

Parameters
Ammo 0
Nitri 0
Nitrate 10
Po4 haven’t tested
Temp 89-90F(lagoon is 85-86F)
Sal 1.025

https://www.reef2reef.com/threads/what-is-killing-my-clowns.979091/

xiongsy · Apr 11, 2023

Temp is good imo. Are both tanks connected?

Jonathan lee · Apr 12, 2023

xiongsy said:
Temp is good imo. Are both tanks connected?

Tested temp today with temp pen, it never passed 30c. So my glass thermometer probably isn’t accurate since it shows 32c.

They are not connected. Two systems. Anyway i just lost the last fish just now. Im taking the system down tomorrow and restarting it. I saw ALOT of white stringy poop at the bottom of the tank. Dosed prazi as per instructions and fish died hours later. This fish has been thin for 2 months now and ive been treating with prazi(twice already today was third) and general cure laced pellets. It eats 5 times a day but will never put on weight. But its very active and comes up for food. White stringy poop had been seen since 2 weeks ago when i gave general cure laced pellets.

Currently soaking the bio media in chlorinated tap water to kill anything. Tomorrow the tank and equipment will be bleached then gonna start the tank again

Flux Capacitor · Apr 12, 2023

How many fish die when dosing Prazi? It will lower oxygen levels a lot. You need to make sure you aerating the water heavily when using.

Jonathan lee · Apr 12, 2023

Flux Capacitor said:
How many fish die when dosing Prazi? It will lower oxygen levels a lot. You need to make sure you aerating the water heavily when using.

There was only one small clown in the tank today when i dosed. I’ve dosed prazi 2 times before when there were more fish in there though and they were ok. The return pipe is placed 3 inches ove water level so when water flows back in, it creates alot of bubbles. I also added a pump at the waters surface for more water agitation. Now, the water was pretty cloudy. I doubt a dead 2cm fish will cloud a 20g tank in under 3h. Probably died 1-2h before i came home. Eyes still bright and shiny clear. Could the prazi have nuked the filter? Like cause an ammonia spike?