algae or slime on 2ft tank?!

[diazman]

hi all, i have this very disturbing problem currently on my 2ft tank. the setup are as follow:

low tech 15 watt lighting
no co2

Substrate:
aquarium sand
nisso custom soil

flora:
java fern
us fissidens

fauna:
betta splenders

tried black out my tank for 2 days but "yes BUT" to my horror, the substrate, plant all covered in this white "slime or algae" or what the heck is it..AND THANKS TO THIS THING I LOST ALL MY BABY BETTA SPLENDERS.

couldnt take a picture as i have lost my camera....

should there be any precaution that i should take or???

Edit: i do 20% water change every monday..
help this poor soul

thanks in advance

[JamesCampbell]

What I personaly would do is siphon all the water out clean the tank walls ornaments etc, run the existing filter afew days then clean that out real good. It should not probally effect the nitrogen cycle. Ive done it many times