I have removed half into 2 other tanks so there are only about 10 in the 30 gallon tank. The smaller fish are in their own tank and 4 are in my brothers 30 gallon tank. I do test the water weekly but I have read that they need salt in the water so added some in their mix. I was told daily water changes is very bad but removal of a few gallons replaced with fresh water is better. Do you actually change your water daily? I read weekly so it happens when I clean the sand on the weekends and replace that water which is about 20-30% of the tank.
Also, since adding the sea salt the strange side-way swimming has stopped. But since this was only done by the smaller fish and they are in their own tank it may also be the change in the tank. It's only been a few days so I will have to see over time.
Read up about the nitrogen cycle and fish tanks. Essentially, fish produce harmful waste products, and beneficial bacteria converts the harmful substances into less harmful substances. The big three parameters important to the nitrogen cycle in tanks are ammonia, nitrite and nitrate. Ammonia and nitrite are very poisonous to fish. They cause those funny swimming problems, death, and other permanent harm. I would venture to guess your gouramis' lifespans have been drastically shortened by the conditions you have exposed them too.
Nitrate is not as harmful as ammonia and nitrites, however it can cause problems in high levels. You need to get a liquid test kit to check all these parameters. Those strips they sell are inaccurate and therefore useless. Since your tank has very little beneficial bacteria as it is newly set up, ammonia and nitrite are going to build up. I suggest daily 50% water changes as you need to keep the ammonia and nitrite levels under .25 ppm. Given your ridiculously high bioload I would not be surprised if you had to do more than one water change a day.
Contrary to the myth floating around, frequent water changes absolutely do not harm your beneficial bacteria colonies. The bacteria grow on surfaces, and do NOT live in the water column! Frequent water changes will slow the cycling process in aquariums, however. The higher the ammonia levels (within reason), the faster the bacteria can grow. Since you are in the middle of a cycle involving fish, you
must do the water changes to spare their lives. You can see how ugly this is--as you are prolonging your cycle in order to save your fish. And a longer cycle=even more stress on the fish. A lesson to learn is never ever do another fish-in cycle again! Cycling a tank without fish is much faster, as you can keep high ammonia levels without subjecting living creatures to poison.
You mentioned you had friends with aquariums. If your friend has a healthy tank devoid of parasites or other nasties, you should borrow some of their filter media and put it in your filter. The media will have the bacteria you and your fish need. (Don't take all of his media, or then his tank might plunge into a cycle. Never ever throw out your filter media without first seeding new media) Go over to his house with a plastic baggie, scoop up some of his tank water and a put a portion of his media in the baggie. The idea is to keep the media wet in tank water until you can get it home. (dry media=dead bacteria, tap water=chlorine=dead bacteria)
Since you have removed a number of the fish from the aquarium, you risk a lot of harm returning them all at once to your aquarium. The bacteria colonies only grow to the bioload you have, so a sudden large increase in bioload will result in more tank cycling. In other words you will return to step one and your tank will be a filthy cloudy mess. I don't mean to be blunt, but you ought to take the majority of your gouramis back to the fish store. They grow fairly large and even females can fight amongst each other.
Read some articles on proper tank stocking. And I don't mean go to yahoo answers or the first page google returns. I hope I've made it evident that there is a lot of wrong information circulating about fish care. Consider joining a fish forum, or lurk on some to glean knowledge. What ever sources you are using for information now seem to be very misinformed. (Take for example your addition of salt. You mentioned you read salt can help. While it might temporarily relieve the painful symptoms of nitrite poisoning (i.e. funny swimming), it will
not get to the root of the problem. Water changes are the correct solution)
If you have any more questions please don't hesitate to shoot me a pm.
