Summer Coral Care — Heat Management Guide

The Greatest Summer Threat to Corals: Bleaching

Coral bleaching risk increases dramatically when water temperatures exceed 28°C. Bleaching occurs when zooxanthellae, the symbiotic algae within coral, leave due to stress. If prolonged, the coral will die. Japanese summers regularly see room temperatures exceeding 35°C, making coral keeping without an aquarium chiller extremely dangerous.

Once bleaching begins, it progresses rapidly. Coral that has completely lost its zooxanthellae cannot produce nutrients on its own. Early-stage bleaching may recover if water temperature is returned to the proper range, but prolonged exposure leads to irreversible tissue death. Daily water temperature checks are essential—act immediately upon noticing any changes.

Choosing an Aquarium Chiller

Aquarium chillers come in inline and drop-in types. Inline chillers connect to external filter plumbing and offer high cooling efficiency, recommended for tanks 60cm and larger. Drop-in types are designed for smaller tanks with easy installation but slightly lower cooling capacity. Choose a unit with capacity exceeding your tank's water volume.

When selecting a chiller, choose a model with cooling capacity one tier above your actual water volume. Considering heat from lighting, pumps, and room temperature, catalog specifications at the limit may not keep up. Plan installation space in advance and ensure exhaust heat ventilation to prevent room temperature from rising.

Fan Cooling and Lighting Adjustment

Using cooling fans as supplementary cooling achieves 2–3°C water temperature reduction through evaporative cooling. However, increased evaporation requires vigilant top-off and salinity management. Additionally, shortening lighting duration by 1–2 hours in summer reduces heat and light stress.

Beyond shortening lighting time, reducing light intensity by 10–20% is also effective. LED lights with controllers allow fine adjustment. While coral coloration may change slightly, reducing bleaching risk takes priority. Restore original settings when cooler autumn weather arrives.

Salinity Stability Is Key

Fan cooling increases evaporation, causing salinity levels to rise. Check with a refractometer daily and perform frequent top-offs with RO water. Stabilizing both water temperature and salinity is the key to successful summer coral keeping.

An Auto Top-Off (ATO) system automatically replenishes RO water based on evaporation, greatly contributing to salinity stability. This is especially worth considering for those away during the day, as manual top-offs alone may not keep pace.

Intensified Summer Water Quality Monitoring

Summer temperature increases cause biological activity changes in the tank, making water quality parameters unstable. KH (carbonate hardness), calcium, and magnesium consumption may fluctuate, so test more frequently than usual.

For SPS (Acropora, etc.) tanks particularly sensitive to water quality changes, testing 2–3 times weekly provides peace of mind. When abnormal values appear, avoid large one-time corrections—adjust gradually to minimize coral stress.

Finding Healthy Corals on Buri-Choku

On Buri-Choku, you can purchase corals carefully raised by trusted breeders. The ability to consult directly with breeders about care environments and management methods is a major advantage.