your problem is a high nitrate level, thats what the algae is thriving on.
there are chemicals to combat this, but personally i wouldnt use them.
your best attack is to plant more live plants (these will use the excess nitrate and cut down the light that the algae receives) and change 25% of the water every week.
basically treat your enclosure like a fish aquarium, your tank is suffering from a 'cycle'.
LOL ok there buddy
Nitrates are not necessarily the cause of algae. An algae colony need only reach critical mass before it starts to divide and populate at an alarming rate.
You have algae on a divider covered with silicon and sand. Crappy. If it were just glass I'd say grab a razor, scrape it off, and bob's your uncle.
Is this divider siliconed into place?
I can't think of an algae eater that will eat algae and not be murdered by the toxins the toad puts out.
I personally wouldnt really worry about the algae as its presense is in no way detrimental. If it really really pissed you off, you could take the filter (if any) out, the water out, and the toad out. Cover a cloth with hot water and salt (about 1/3 salt) and tap away at the divider. THe algae will die on contact with this concentration of salt and rub off. Make sure you wipe away all the residue after with clean water. You don't want to get salt on your toad, and you dont wanna shock your good bacteria when you put the filter and water back.
Obviously dissolve the salt in the water first. Duh.