As its a Fluval Edge stick it right in the middle on the back glass, the back casing/filter will camouflage it and then use rocks/wood/plants to hide it. Lets remember this is a Fluval Edge that will have at the most £20 of basic fish in it and not a reef costing £x000. A standard heater is perfectly fine, you absolutely do not 'need' a controller. The dosage on the bottle is conservative, just dose it in full strength. But just doing liquid carbon isn't a magic 'cure all' and doesn't address the root cause. Water changes and tweaking light/fertilisers are the best way of dealing with algae in a sustainable way. Dosing liquid CO2 could make it worse if the problem is a lack of available nutrients. Dosing instructions on aquarium fertilisers is generally based on low light, light to moderate planting and no CO2, you will certainly need to dose more if you start using liquid CO2.