my fish die die die

Question
I've bought guppies last year. 20 of them and all of them died. I'm not sure what happened. Their tails begin to rot? or being bitten. slowly they lost their arms... fins..tails.. everything! and they die. Ahh!! I can still remember how hard I cry looking at them like that.

So I decide to buy fishes with short tails. Which is barb (the fishman said its a tiger barb??) 5 of them. I mixed with plato fish and 1 cichlid (i'm not sure if its a cichlid but it does look like one) with 5 small fish around 1.5 cm. I don't know what is its name but it is brown and has black tail. (I'm sorry but I'm not good in fishes)

The BIGGEST problem here is, my aquarium seems to divide into 2. The cichlid took the left side and all other fishes moved to the right. I think the other fish have problem with space (which cichlid WILL NOT HAVE because he has SO MUCH SPACE). 1 by 1 died. All my plato fish died (I don't know why). They seem to stick at the filter or just die without scratches on their body. 4 OF MY TIGER BARB DISSAPEAR!!! Which means they died. and 1 of the tiny cute fish stuck at the filter (again)

So... is it because of the filter, or the cichlid or... disease?

I'm planning to bring out the chichlid into a [goldfish] bowl. Will he survive in a bowl?
Then If he CAN survive, I hope I can buy some goldfish, but I'm afraid of the tail rotting / bitten again. Will Tiger barb and the tiny fish attack gold fish?

and... i have a sucker fish ... the fish that sticks at the glass and everything?... you know? erm... HES so lazy that he don't suck anything and he eats fish food..... is that how it works? My friend's sucker fish eats the brown things on the plastic plant and glass but mine dont!! did i bought the wrong one?

Answer
Hi Soely,
It can be very difficult to know exactly what happened with all those guppies you lost. It could have been anything from water quality to diseases like Finrot.

*Now with your other fish the cichlid's behavior is normal. Most all species of cichlids are very territorial and often want to take over a space in the aquarium and keep any other fish cowering in the corner. Cichlids don't particularly belong in community tanks unless they are a known peaceful species such as Angels (and even then! ;-)

I hate to get your cichlid in trouble, but I wonder if he is responsible for a lot of the fish loss you've had, who knows. He may be doing a lot of the dirty work. As for the fish just dying for now apparent reason, that makes me think of water quality issues. It helps tremendously to know your ammonia, nitrite and nitrate levels as well as your pH. As a rule, ammnonia and nitrite should always be ZERO in order for your fish to be healthy. And nitrate should be 20 or less. The pH level is not particularly important but it should just be stable and not too low (not below 6.0) but otherwise most fish are very adaptable and are able to thrive in a big range of pH levels.

I don't think its your filter. Many times it looks like the culprit for fish loss is the filter because dead or dying fish easily get siphoned to the strainer but that is only because they were weak already from some other cause. It could be the cichlid, water quality, or disease. We will have to narrow it down one by one to figure out the real culprit. The first thing I'd do is test your water and make sure your ammonia and nitrites are ZERO and nitrates are not too high, if ammonia and nitrites are present then that means that your beneficial bacteria colonies have not established yet or have been disturbed by an filter overcleaning, medication usage, ect...You'll need to start doing very large water changes (50% or more) to keep your fish safe and to lower the ammonia and/or nitrite level. With time the bacteria would establish and control these levels and keep them at ZERO.
Then determine if any of the fish look sickly, if they have any spots, markings, discolorations, ragged fins, heavy breathing or any other stress symptom. If they all seem to be doing good and they have clear eyes, good colors, clean fins and smooth scales without any spotsor markings and they are behaving as they should for their species than the next thing to consider is in fact the cichlid of course. He may be stressing everybody out to much and he may be eating some of your fish as well. I'm curious to know what kind of cichlid this is.. Maybe if you could describe him to me I could probably identify him.

The cichlid probably wouldn't do very well in a bowl at all. The water quality would be horrible in no time. You might want to see if you can return him to the petstore or get somebody else to take him for you.

Tiger barbs will in fact be fin nippers and shouldn't be kept with fancy finned fish. You should also make sure you always keep them in groups of minimum 6 or more so they have  plenty of their own kind to interact with and they usually will leave other fish alone.

As for the sucker fish (maybe he is a pleco or a chinese Algae eater?) its normal for them to behave as your is. They are very docile fish, spending their days sticking to the glass, bottom, or on the tank decorations and only occasionally moving around the tank to find another place to stay suctioned to or to search around for food. Just plain fish food isn't always the best diet for sucker fish like plecos. They should really have algae wafers, zucchini slices and romain lettuce dropped in their tank (secure the vegetables with an aquarium plant weight) at night when lights are off. Otherwise if they are left to fend for themselves on just fish flakes then they can suffer from poor nutrition and sickness.
But otherwise, sucker fish can be rather lazy at times. Some species are more active than others. But common plecos are very docile and quiet fish for the most part.

I really hope this helps and best of luck with everything!
Karen~