What is this skin-like algae growth?
I have a 95 l Kent Marine tank, holding hammer, mushroom and gorgonian corals, along with a hermit crab, two Nassarius snails, and two Turbo snails. The set-up is now four years old, and until about eight months ago the system looked beautiful, but I now have what looks like an algae, which is dark brown in colour, covering much of the live rock. I can only describe it as a skin-like covering, which, with the aid of tongs, I am literally able to peel off in small sheets. This skin entraps oxygen, as I see countless bubbles under it, and really does look unsightly. Fortunately to date, it has had no adverse effect on the corals or livestock.
I’ve tested all the usual water parameters, and also had a water sample tested at a local store, and each result has been normal, apart from the hardness being a little too soft.
I do regular water changes and so on, but it just looks a such a mess. I’ve tried in vain to determine what this growth is, both online and talking to fish shop staff. Any suggestions would be gratefully received.
STEPHEN HOLMES, VIA EMAIL
JEREMY SAYS:
The algae sounds like dinoflagellates. This is an opportunistic ‘algae’ which is usually more prevalent in new tanks, but it can appear in established reef systems as well.
My guess is that something changed in the tank eight months ago, allowing the algae to take hold. Has the nitrate level changed? Did you have a skimmer and then remove it, or vice versa? Did the pH change, or the temperature?
There are bottled solutions like Fauna Marin’s Dino X, but I would combine it with a few weeks of increased maintenance that include scrubbing all the rocks with a toothbrush, scraping the back glass with a blade and syphoning out as much as you can.
I would consider changing at least 50% of the water every week during maintenance, and ensure mechanical media is cleaned regularly and a high flow rate from a wavemaker is maintained. Boost that carbonate hardness with a liquid buffer and make sure it stays at a nice constant 8°KH. Test pH too as it should be 8.2. The lights may have degraded over four years, so it’s probably time to consider replacements.
Unfortunately, no algae grazer will touch dinoflagellates so it’s all about maintenance and finding an alternative treatment. It might also be worth turning the temperature up to 82°F for a few weeks, as reefkeepers in the US have found it to be a useful cure.