Your tank doesn't look incredibly dirty to me. Water changes are vital despite what the tank looks like, though.
A tip about cleaning the silk plants, I've found that boiling water and dumping it over them (while OUTSIDE the tank) will get rid of that brown algae right quick. Anything that doesn't die off immediately can be quickly taken care of using a toothbrush (never been used, obviously).
As far as 100% water changes, I try to do them about once a month (my tank is heated and filtered), just to get all that really gross stuff out of the gravel that gets stirred up during my usual 40% weekly changes.
A tip about cleaning the silk plants, I've found that boiling water and dumping it over them (while OUTSIDE the tank) will get rid of that brown algae right quick. Anything that doesn't die off immediately can be quickly taken care of using a toothbrush (never been used, obviously).
As far as 100% water changes, I try to do them about once a month (my tank is heated and filtered), just to get all that really gross stuff out of the gravel that gets stirred up during my usual 40% weekly changes.
