For the current situation change 60% of your water and make sure you clean your filter completely and then follow the below:

 

* Change 25% of your water every week

* Calculate the length of each fish (in inches) and add it up and then make sure it is less than the Gallon volume of the tank (For example;5 fishes of 5 inches each would make 25 inches; so your tank should not be less than 25 gallons)

* Use AZOO Tank Auto filtration Liquid (2 Bottles in one pack for chemical and Bio filtration) It really helps, Available from a shop called Golden Fish in Najma and maybe elsewhere too.

 

Have 2 Tanks with Big Oscars, 1 foot Catfish, Angel fishes amd lots of live plants, and 2 kid mollies.

 

And you dont need an external filter, even with builtin filters you can maintain your tank in best conditions.

 

Anyone Having Unused Tanks please PM me...I need more tanks...

 

Any more questions; contact me.