Dosing nutrients for an improved macroalgae growth in the planted display tank and planted refugium
As everything in the marine aquarium, stability is the key to success for a good macroalgae growth too.
To maintain proper nutrient / mineral levels in the marine aquarium will ensure that the macroalgae can grow effectively and do its best, removing unwanted nutrients from the marine aquarium water, as it will with its growth take out the Nitrate and Phosphate for a more clean aquarium water environment.
(Of course the beauty of some macroalgae species is not to undervalue too :))
All macroalgae species and especially the fast growing algae species like Chaetomorpha and Caulerpa will need beside Nitrate and Phosphate some other so called major and minor minerals to maintain optimal growth conditions.
You can find more information about what minerals macroalgae will need to grow well and what are the best water conditions for macroalgae HERE.
As macro algae will not just take out Nitrate & Phosphate from the marine water for a more clean aquarium environment, algae will consume as well other minerals like Magnesium, Calcium and Potassium too which are important for other tank inhabitants like hard and soft corals.
It is therefore important to replace those consumed minerals to maintain a stable water quality.
Light Planted Reef Display Tank or Refugium
It will normally be fine performing regular water changes in a marine aquarium with just a few macroalgae species in the display tank or refugium along with the presence of livestock, like fishes or Seahorses as they will will often provide enough nutrients for a good macroalgae growth ( fish poop ).
Should you however experience problems with the growth of your macroalgae, or when the algae decomposes it might be beneficial (assuming you have suitable lighting conditions for the macroalgae to grow) to dose extra minerals to support a healthy macroalgae growth again and keep the nutrients levels in the marine aquarium balanced.
An easy solution to dose minerals are ready mixed multi-nutrient solutions (aka fertiliser) like ChaetoGro from Brightwell Aquatics, which is especially formulated for the use in the marine aquarium as it is Nitrate & Phosphate free, plus it does not contain any Copper.
Unfortunately most available fertilisers for the planted aquarium are designed to use in freshwater aquariums and therefore include Copper, as this is an important mineral for freshwater plants. But as macro algae are not plants they will not need copper to grow.
An easy solution to dose minerals are ready mixed multi-nutrient solutions (aka fertiliser) like ChaetoGro from Brightwell Aquatics, which is especially formulated for the use in the marine aquarium as it is Nitrate & Phosphate free, plus it does not contain any Copper or Continuum's Basis Chaeto Grow, which is well Nitrate & Phosphate free.
Copper can be toxic to aquatic animals and invertebrates like shrimp and snails as they are particularly sensitive and should be avoided in the marine aquarium. As the amount of Copper in Flourish® and TNC Complete / light is very small it would be a massive overdose necessary before it would begin to reach an amount of Copper that is toxic to animals and invertebrates. This said when using those fertilisers we recommend for safety reasons to measure regularly the Copper level in the tank water and to use if necessary Copper removing supplements.
Heavier Planted Reef Display Tank or RefugiumFor more heavier planted marine aquarium display tanks and planted refugiums it may be necessary to add Nitrate and/or Phosphate to maintain a recommended level of at least 3-5 ppm Nitrate and 0.01 ppm Phosphate, especially when using Brightwell Aquatics ChaetoGro, Seachem Flourish comprehensive or TNC lite.
Therefore, for low nutrient tanks TNC offers the TNC Complete Aquarium Plant nutrient fertiliser which includes Nitrate & Phosphate (but as well a very small percentage of Copper ).
Overview of the ingredients from different Fertilizers for Planted Tanks
*1 = 1% Nitrogen (N) calculates to 4.427% Nitrate (NO3)Important: Continuum does not communicate the ingredients of its Basis Chaeto Grow fertiliser.
*2 = 1% Phosphorus (P) calculates to 3% Phosphate (PO4)
*3 = 1% Phosphate (PO4) calculates to 0.7473% Phosphorus Pentoxide (P2O5) as listed in Seachem Flourish
*4 + 1%Potassium (K) calculates to 1.2% Potassium Oxide (K2O)