Algae problem.

[Gary Douglas]

I wonder if you could help me identify/ eradicate the algae outbreak in my tank at the momement. My susbstrate and reef become covered in air bubbles and a fast growing
brown hair like algae covers everything. I have syphoned it of regulary but it comes back fairly rapidly. My tank has been running for 2 years. It is 200 litres with a trickle filter using matrix, 2 x 40w actinics, 1 x 40w coralife,
1 x 150w metal halide ( 4000 kelvin only), 40 kilos of live rock, Protein skimmer. My water chemistry is always o.k with Nitrate being the only exception ranging from 10 to 20 ppm. The outbreak started approx 3 weeks ago. The metal halide has been in service about 5 weeks. About 4 months ago my supplier changed their synthetic salt brand so I dont know if silica could be a cause.

[rshimek]

Hi Gary,

[welcome]

The root cause of algal outbreaks is an accumulation of excess usable nutrients. Your data with the high nitrates indicate that is the case in your system.

The solution is to remove the excessive nutrients; but unfortunately, that is lot easier said than done. Nutrients enter the tank by feeding and leave only through exportation. The ways of exportation are through 1)water changes, 2) denitrification (removes nitrates only, not other nutrients like phosphate), 3) biomass export (removal of excess algae which have accumulated nutrients) and 4) skimming (both skimmate and skimmer sludge contain high amounts of nutrients.

You need to consitently pull out nutrients as you cannot reduce feeding (most of our animals are marginally fed, at best). Generally, trickle filters are not considered to be effecient methods of denitrification (other filter methodologies are generally better). You might consider changing the filter method.

Alternatively or concurrently, you might consider upgrading to skim the system as much as possible.

Additionally, you might consider growing some fast growing macroalgae somewhere in your system to help suck the nutrients out of the water. Periodically, these algae may be harvested and discarded.

Finally, continue siphoning out the algae that are growing on your substrate.

Control of nutrient balance is about the hardest part of keeping these aquaria, and unfortunately, it is not easy.

Good luck!! :D