I have 5 10gal NPT's....they work great.....mine range from 1gal to 75gal...if it holds water you can plant it.....I don't use filters long term in my 10gal NPT's-Once mature in about 3 months I remove the filter.
It is best to treat in a small QT container using premixed treatment water so that you have more control and ease of observation.
For tattered fins-often the environment is the cause and by QT'ing this can help rule that out-if he doesn't have fin rot-just fresh, dechlorinated, like temp water and water changes is sometimes the best treatment.
Why are you needing to add salt-generally if you need to treat the Betta it is best to remove them to QT and treat with premixed treatment water.
Some tetras can be sensitive to salt in therapeutic doses needed to treat a Betta
Hey OFL! I'm not sure if i'm asking the right person but I'll ask anyway. So,i wanted to start putting aq salt in aqua's (betta) 10 gal tank. But in there are 6 penguin tetras and according to some members, they say that salt makes water hard and tetras are from soft water environments. But when I look on different sources on the internet, it says that it is ok to put salt in the tetras tank. I am very confused. Do you think I am able to put salt in or no? Also, if I can , what is the best way to adjust the fish to a rather "salty" tank?