I can only give my experience from owning an allotment and having one of these. There are black IBC's available online which will pretty much eliminate algae growth and if you're lucky enough to spot one on an ind. estate around you it is sometimes worth asking around for any that are going spare (free) or for a small fee. Just be careful as some of these IBC tanks can hold various chemicals which might need a thorough clean before use.
Also, 1000 litres of water is about 1 tonne in weight so make sure the footprint it is on is sufficiently supported and not on your favourite patio slabs which may crack under the weight.