Major Problem With New Tank

[inthisday]

Hello frist of all.

i have had my tank now for about 3 months had plants set up for over a month then added 9 tetras and 3 danios. 2 weeks later i added 3 more tetras and 2 danio. Then a further 2 weeks i added 1 siamese, 2 gouramis, a plec and a cloan loach to take care of my snail problem as by then i only had a few plants left. So a week later is when it all goes wrong i started to notice my siamese loosing most of his tail fin as if it was rotting away with large like scar patches on him. then the following day a skeleton no fish. then almost 11 hours later 3 dead tetras 1 dead danio. all showing the large scare symptom but no fin loss, and now one of my best gouramis has a rather painfull looking saddle sore i would say like a large white scar and its now struggling to swim propperly. also 2 of my tetras also have the large white patches as if the scales have come off. I am assuming its to do with nitrates or ammonia levels as im very new to the fish keeping business. but i am extremely worried about the rest of my fish now. any ideas what it is? also not able to test the water yet due to it being 9pm here no pet shops open yet =(. im just hopping my guys last till the morning


thanks in advance mike. also will try upload a picture of my poor gouramis

 

[Baccus]

So the tank was set up for 3 months and in the 4th month you added fish?.
The first question everyone will ask is did you cycle the filter? And how, eg adding ammonia to get filter bacteria living and working.
If the tank/ filter was not cycled then adding 9 tetras and two danios is a massive strain on any filters biological control.
The siamese fighter losing his tail could have been down to poor water quality but I would also suspect the gouramis and the fighter, fighting they really are not compatible fish.
Also you didn't mention what sized tank you put all the fish into, depending on the type of pleco they can get huge and clown loaches also get huge and are extremely social and will be more prone to stress illnesses being on its own.
Sorry to not be able to give you some more help, but you have come to the right place.

 

[inthisday]

the filter was given to me by a friend who got a larger tank. the tank is 120 litre tank and i got a bristle nose plec was told by the peeps at pets at home he would be ok and the clown loach i was hopping to add 1-2 more at a later date once it had all settled, and was told it should be fine to have the tetras and danois in as they are hardier fish. but i guess i made a over under estimate there . i also forgot to mention for the first month after the tank was set up with all the plants i did have about 30 plants which is now down to 4 elodea i believe they are. im new to this but i imagine the massive loss in plants would have a huge detrimental effect on the tank and a month before i added the gouramis, fighter and loach. everyone was doing amazingly all looking great and doing great. it all seemed to happen when i added the extras. also here is a picture of the 2 problem fish as all the others now seem to be fine *fingers crossed* but i guess i will see in the morning.
To note i also just noticed a white substance on my gravel as i was taking the photos.

 

[Baccus]

The white stuff on the gravel is a type of mould which is most likely growing on organic waste.

The gourami, looks to have a particularly nasty fin rot. Saddle on the tetra I am not sure about but might pay to look up neon tetra disease.

Yep a bristlenose should be fine in 120L, so your lucky there

. However I think 120L is really to small for eventually 3 clown loaches.

Many of the common tetra species that are mass farm bred actually have weakened immune systems and are now often a sickly fish. Also tetras do best in well aged/ established aquariums.
Danio's however are generally a hardier fish and are often used for fish in cycling of filters.

Do you know what the other plants where? Do you by any chance have pictures of them before they died? Many shops sell non-aquatic plants as aquarium plants and the plants end up only rotting away which would cause major water issues. Also clown loaches are natorious plant eaters and destroyers, so he may have had a hand in the final demise of already struggling plants. Even the bristle nose will have a good go at plants if the mood/ need takes them.