marine fish tank, rocks gone red

Question
Hi

My marine tank seems to have a red tinge to it.  All the rocks have gone red.  Do you know what could be causing this and what can I do please?

Answer
Hi Janet. Is the water actually tinged red or is there a film on the glass that gives it a red appearance? Is it slimy or dusty in appearance on your rocks? Without a better description it is very hard to diagnose this problem. However it may be a cyanobacteria bloom otherwise known as a slime algae bloom. Slime algae forms tissue paper looking films on any surface in the aquarium. It usually blooms in aquariums under organic nutrient rich conditions and is very fast growing. Controlling this outbreak is very difficult if changes aren't made to prevent its growth. Check your water quality. High nitrates and phosphates promote this algae. Make sure you are changing your filter media and /or rinsing it frequently. Check your lighting too. Use only bulbs designed for a saltwater tank and change them at least every year. Good water flow and the use of a good protein skimmer and activated carbon can help. Also siphoning the algae off of gravel and rocks is also needed in order to control it. You may want to do small frequent partial water changes using distilled or reverse osmosis water to mix with your salt as well. If all else fails I have had good luck using an additive called chemiclean to rid a tank of this problem. This will remove it but if you don't fix the water quality than it will be back and may become immune to chemical treatment. However if this doesn't sound like what you have going on in your tank then get back to me with a better description and what your water tests at and I can assist you further.