There are a few problems identified here.
First is the number of fish in a relatively small (100 liters, or roughly 25-6 gallons) tank. You don't give the numbers, but some of the mentioned species are shoaling fish which means they must have a group. Most sources will say six is minimum, but sometimes this is not sufficient...but you have to consider the tank space. Shoaling fish that are not kept in reasonable sized groups usually react with increased aggression, to each other and/or the other species. Tetras are shoaling fish, and the Black Widow/Black Skirt is a feisty (= aggressive) species prone to fin nip. Danio species are also shoaling; some catfish are as well (you don't mention what you have). And the groups must be of the individual species, so for example 6-8 zebra danios, 6-8 Black Skirt Tetras, 6-8 Neon Danios. These numbers are only basic guides, you haven't room for all of these fish, so some will have to be removed.
Second problem is temperature. "Tropical" fish do not need water anywhere near the temperature you mention of 28-30 C. This is much too warm for the species mentioned. Fish are ectothermic, which is commonly called "cold-blooded." This means that the temperature of the water in which they find themselves governs their metabolism. Their internal functions operate according to the temperature. This is much too involved to go into in detail, but I can say that as the temperature increases, the fish's metabolism works harder, much harder, and this literally wears the fish out. They will be stressed, which means their immune system is weakened, so they are more likely to get diseases that they would (should) otherwise fight off easily. They likely will become more aggressive, though this varies. Point is, keep them in the lower mid of the recommended range for the species, and each species has its range.
Water parameters were mentioned by one member but not answered. Hardness is critical to fish, some need harder water (containing more dissolved minerals), others the opposite, some manage roughly in between within reason. Mollies must have harder water than any of the other species mentioned in post #1. Without knowing the GH I can't offer much more on this.
Some of the fish are not going to work long-term in this tank, given the space and the other inhabitants. I don't know what "algae eaters" refers too, but some of these are trouble. "Sharks" are always likely to be problematic, and these two should go elsewhere. And before it is said, the fact that for several months things seemed to you to be working does not mean they really are in the best interests of the fish.
Byron.
First is the number of fish in a relatively small (100 liters, or roughly 25-6 gallons) tank. You don't give the numbers, but some of the mentioned species are shoaling fish which means they must have a group. Most sources will say six is minimum, but sometimes this is not sufficient...but you have to consider the tank space. Shoaling fish that are not kept in reasonable sized groups usually react with increased aggression, to each other and/or the other species. Tetras are shoaling fish, and the Black Widow/Black Skirt is a feisty (= aggressive) species prone to fin nip. Danio species are also shoaling; some catfish are as well (you don't mention what you have). And the groups must be of the individual species, so for example 6-8 zebra danios, 6-8 Black Skirt Tetras, 6-8 Neon Danios. These numbers are only basic guides, you haven't room for all of these fish, so some will have to be removed.
Second problem is temperature. "Tropical" fish do not need water anywhere near the temperature you mention of 28-30 C. This is much too warm for the species mentioned. Fish are ectothermic, which is commonly called "cold-blooded." This means that the temperature of the water in which they find themselves governs their metabolism. Their internal functions operate according to the temperature. This is much too involved to go into in detail, but I can say that as the temperature increases, the fish's metabolism works harder, much harder, and this literally wears the fish out. They will be stressed, which means their immune system is weakened, so they are more likely to get diseases that they would (should) otherwise fight off easily. They likely will become more aggressive, though this varies. Point is, keep them in the lower mid of the recommended range for the species, and each species has its range.
Water parameters were mentioned by one member but not answered. Hardness is critical to fish, some need harder water (containing more dissolved minerals), others the opposite, some manage roughly in between within reason. Mollies must have harder water than any of the other species mentioned in post #1. Without knowing the GH I can't offer much more on this.
Some of the fish are not going to work long-term in this tank, given the space and the other inhabitants. I don't know what "algae eaters" refers too, but some of these are trouble. "Sharks" are always likely to be problematic, and these two should go elsewhere. And before it is said, the fact that for several months things seemed to you to be working does not mean they really are in the best interests of the fish.
Byron.
