Ultra low nutrients; associated nuisance algaes and coral health

5 Minute read

Ultra low nutrients; associated nuisance algaes and coral health

Running your reef aquarium with nutrients as low as possible has always been the goal for the home reef tank. Closely replicating the water quality found in natural reefs and oceans makes perfect sense when keeping animals in their natural environment.

A distinction between nutrients and nutrition must firstly be explained. As although corals have the ability to assimilate (absorb) nutrients like nitrate and phosphate directly from the water column this can be difficult at times for the coral organism. They also consume nutritional particles when feeding. This includes everything from bacteria to small food particles missed by fish. They are consumed through the mouth of the coral and then digested where energy and nutrients are better integrated into the coral system. Coral will typically feed and dawn and dusk this occurs during the diurnal migration of plankton from deeper water up to the shallows and back down again.

Natural reefs have vast quantities of plankton and bacteria that the corals will feed on regularly however the nutrient value in the water column is almost imperceptible on our standard hobby test kits, even some of the most sensitive testing methods using mass spectrometry will struggle to pick up any reliable levels of nitrate and phosphate in the water column.

A recent trend in the aquarium hobby has been to increase the nutrient level of an aquarium which for some tanks that are classed as ‘super clean’ this can have a beneficial effect. Many stop there as they are getting the results they desire. Understanding what this is doing to your aquarium ecosystem is very important and can let you fine tune and change your approach to this method to get better results. Some issues that have been associated with elevated nutrient levels as low growth speed and increased mortality for newly introduced or specifically sensitive species. Although the benefits include increased colour and decreased mortality in certain situations.

Increasing nutrients in your aquarium typically nitrate over 20ppm and phosphate over 0.1ppm indirectly fixes a lack of nutrition in the aquarium. Corals are lacking particulate food matter as well as consumable bacteria. Giving the corals an alternative path can counteract the effects of a lack of nutrition.

Ultra low nutrients have another effect that is often the biggest complaint associated with these aquariums. The ecosystem of your saltwater tank relies on bacteria to breakdown detritus and harmful base waste products such as ammonia. The bacteria extract the nutrition that they require from those compounds and release different compounds culminating in the release of nitrate and phosphate. While some anaerobic bacteria can break nitrate down further into nitrogen gas this requires a certain level of bacterial activity to create areas of low oxygen within rock and ceramic media. The issue with Ultra-low systems is the lack of bacterial activity. This is the main cause of nuisance algae. The bacteria would typically out compete the algae for nutrient availability as well as spatial restrictions on the surface of rocks.

There is a simply way to combat this issue by dosing small regular amounts of controlled nitrate and phosphate (increased feeding can also do the same if this has been reduced). Dosing just enough nitrate and phosphate that nutrient levels in the aquarium don’t increase by more than 20% will give more bioavailability of nutrients to bacteria. The bacteria will rapidly increase occupying more surface area in the aquarium outcompeting nuisance algae. Another benefit of this increase in biological activity in the increase amount of waste compounds and bacteria in the water column which the corals will directly feed on negating the coral animals’ nutritional deficiency.

Although this seems like a simple fix it takes time to increase the biological activity and can be a fine balance between too high nutrient levels which can cause other algal issues. It can be very beneficial to add addition bacterial supplements into the aquarium this can increase the diversity of bacteria within the aquarium as well as help maintain a healthy population combating natural population health declines. Additional bacteria can increase the speed of recovery and if nutrient levels stall and increased levels the bacterial supplements will kick start new biological pathways with the aquarium ecosystem.