Dragging up an old thread, but i can add what it cost me in pounds, includes the stores i purchased from:
Initial Purchases
Tank & Stand - £130 - 10UK Gallons (freshwater cube) - Pets at Home
Powerhead - £27.99 - Maxijet 1200PH - ebay
Salt - £12.99 - Tropic Marin Pro Reef Salt 4KG - Local LFS
Bucket - £0.99 - ASDA Supermarket
Measuring/Mixing Jug - £0.50p - ASDA Supermarket
Saltwater Test Kit - £17.99 - PH, Nitrate, Nitrite, Ammonia - Local LFS
Hydrometer - £15.99 - Instant Ocean - Local LFS
Thermometer - £10.99 - Digital Thermometer - Local LFS
R.O water - £6.00 - 50 Litres - Local LFS
R.O water containers - £5 x 2 (£10) - Local LFS
Heater - £17.99 - Visitherm 50w Heater - Pets at Home
Algae Scrub - £1.99 - Local LFS
Total "Required" Purchases = £253.42
Live Rock & Sand
Sand - £12.99 - Aragonite - Local LFS
Live Rock - £60 (approx) - 6KG Fully Cured Live Rock - Local LFS
Total Live Rock and Sand = £72.99
Optional
Lighting (2x 18w T5 Tubes) - £7.95 x 2 (£15.90) - coralgarden.co.uk
Starter Unit for 18w T5 (already had one in hood) - £17.95 - Interpet - coralgarden.co.uk
Rowaphos (phosphate remover) - £7.99 - Local LFS
Additional Heater for water changes - £10.99 - Cheap 25w Heater - Local LFS
Additional Bucket - £0.99 - ASDA Supermarket
Total Optional = £53.82
Overall Cost = £380.23
Please bear in mind i do not run a skimmer or any other filteration bar Live Rock. This is simply the STARTUP costs for a 10UK Gallon Marine Tank, by no means is this what you must have, and you may wish to upgrade from my choices. This does not take into account costs for livestock, replacement water, filters, food, replacement test kits etc.