aggressive

I have three swordtails and one of my females is being mean to my male. My tank has been set up for about a month and is a 36 gallon. Anyone know why they are being aggressive?

I have 5 tiger barbs with semi aggressive fish and only the tiger barbs have white bulgy spots and the fin damage I've used meds for ich and no progress the spots and fin damage have only gotten worse what do I do. (The fish are to fast so why post a blurry pic anyway.

:help::help::help::help::help::help::help::help: hi, just got my 1st tank ( 5gallon). got 2 platies but they attack each other. im worried because they cut each others gills but the male is the bully and i think the female is preggers and so she gets aggressive when bothered. plz help im new...