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Biological Imbalance in Aquarium and causes for Blue Green Algae

Updated: Jun 28, 2022

When the pH levels of the water in an aquarium change, the aquarium becomes unbalanced. This results in water quality decline and other toxicities. What causes this to happen?

cyanobacteria causes in shrimp nano tank
Blue Green Algae
Biological equilibrium is attained when the chemical properties of water - such as hardness, pH, and nitrogen component concentrations - remain constant and acceptable, animals and plants develop and thrive normally, and algae do not endanger other living organisms.

Water pH levels are the most common source of biological imbalance in any ecosystem. When pH levels change, the amount of bacteria in the substrate and aquarium décor is affected and may become insufficient to keep the nitrification processes operating smoothly, resulting in a nitrogen cycle crash, ammonia spikes and water toxicity. Also, trace elements will accumulate at increasing concentrations, causing problems such as cyanotoxins, poisonous algae, and bacterial blooms.

Cyanotoxins are extraordinarily strong toxins produced by some freshwater cyanobacterial blooms. Cyanotoxins-containing blooms can be found all over the world, causing uncommon animal sickness and death, as well as human poisoning from urban and recreational water supplies. Hepatotoxic microcystins are the most numerous and structurally diverse class of cyanobacterial toxins. The generation of hepatotoxins in cyanobacteria is hypothesized to be controlled by a variety of physical and environmental factors, including nitrogen, phosphorus, trace metals, growth temperature, light, and pH.

We recently saw the first signs of green blue algae, the most prevalent type of Cyanobacteria seen in home aquariums. And, in order to eliminate the source, we began by studying several causes to establish what would be causing it in our circumstance.

  1. light availability; there is considerable evidence that differences in light conditions and CO2 levels influence cyanobacterial blooms at the local level via changes in ratios. Light intensity and CO2 factors do not lead to an on-off regulation of cyanobacterial production, but rather allow for fine adjustments. We had the same light on 2 similar setups and only one of them developed cyanobacteria.

  2. water temperature; thermal flow promotes the growth of cyanobacteria, whose buoyancy regulation may allow for vertical movement to get nutrients at the water surface. Might be the cause due to changes in weather temperature, but in our case both aquariums, actually all our shrimp tanks are in a regulated room temperature.

  3. alteration of water flow; slow flow and slow water circulation may help the development and growth of cyanobacteria algae. However in slow flow water the algae has a short duration for propagation and may remain in small spores if other conditions are not met for its growth.

  4. vertical mixing; additionally, when a mixing event occurs in the waterbody, nutrient-rich substrate water is brought to the top by upwelling, enhancing cyanobacteria nutrient availability. So this might be the cause when gravel vacuuming your substrate or changing some decoration or aquatic plants.

  5. pH changes; when compared to lower pH levels and acidic water where Cyanobacteria is not present, alkaline pH values may extend the cyanobacteria bloom time. For shrimp tanks, especially caridina, our pH is on the lower levels 5.5 to 6.5, might be that a pH change happened but it is nothing noticeable for an algae bloom.

  6. nutrient loading; In freshwater ecosystems, low levels of the macronutrients phosphorus (P) and nitrogen (N) are frequently the limiting factor for cyanobacterial growth. Eutrophication, or high N and P concentrations, encourage the production of dense cyanobacterial surface blooms and subsequent water quality degradation. Laos in this case our test shows 0 levels in phosphate and Ammonia.

  7. trace metals: some studies have suggested a direct link between cyanotoxin production and some trace metals, iron, cobalt, copper, manganese, molybdenum and zinc…

From Research, Nutrient enrichment of aquarium water with macronutrients together with changes in temperatures and water parameters undoubtedly contribute to the frequency, intensity and distribution of toxic blooms in the tank, yet it appears that for most of the cyanobacteria, toxin production is a direct function of cell proliferation rate. In addition, the regulation of toxin genes and toxin production by light appears to be universal among cyanobacteria, suggesting a link between toxin production and photosynthesis; however, the precise mechanisms of control remain to be determined.

As a result of examining those aspects, we've come to the conclusion that blue green algae in our caridina shrimp tank is caused by a slight biological imbalance, which is frequently coupled with a free fall in NO3/PO4. This is frequently induced by carbon dosing or a tiny bacterial bloom, in which NO3/PO4 levels fall but gaseous nitrogen levels rise to the point where Cyanobacteria take advantage of the circumstance and fix nitrogen from the water.

Hence, when nutrients decline, Nitrifying Bacteria suffers, and bacterial films thin. Cyanobacteria proliferates, taking advantage of the bacterial films and breaking them down, eventually becoming dominant.

Heavier feedings may break the chain by pushing partiality down to the nitrifying bacteria, but once the Cyano takes hold, regaining balance might be difficult.

So we had to perform a thorough water change as well as gravel cleaning to guarantee that the nitrification cycle resumed properly.

Most important points and maintenance tasks to keep up with in the future:

  1. Keep up with filter cleaning

  2. Be careful with the substrate

  3. Control your cleaning and gravel vacs

  4. Dosing and feeding appropriate amounts and only necessary nutrients based food.


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