Brown Algae (Diatoms)

Clinical Identification

Diatoms manifest as a soft, easily disturbed brown film covering the substrate, glass, and plant leaves.

• Texture: Unlike the hard crust of GSA or the fuzzy nature of hair algae, diatomaceous biofilms feel slimy and can be brushed off effortlessly with a finger.
• Rapid Onset: They are typically the very first photosynthetic colonizers in a newly established aquarium, often appearing within the first 1-2 weeks of cycling.
• Phototropic Behavior: While they require light, diatoms are highly efficient at low PAR levels, allowing them to outcompete higher plants in shaded regions or during the initial "dimmed" break-in period of a new setup.

Etiological Triggers

1. Silicate Abundance: The absolute prerequisite for diatom mitosis is bioavailable silicic acid (Si(OH)4). New glass aquariums, fresh unwashed sand substrates, and certain decorative rocks leach significant quantities of silicates into the water column.
2. Microbial Immaturity: In newly established tanks, the lack of a mature biofilm of heterotrophic bacteria leaves physical surfaces entirely uncolonized and devoid of competition.
3. Ammonia and Low Light: Trace amounts of ammonia (typical of a cycling tank) combined with conservative lighting protocols provide an optimal environment for diatomaceous blooms.

Remediation Protocols

• Manual Disruption: Due to their lack of holdfasts, diatoms can simply be wiped from the glass and vacuumed from the substrate during routine maintenance.
• Silicate Depletion: Chemical filtration media containing iron oxide hydroxide (GFO) or specialized silicate-absorbing resins can rapidly strip the water column of Si(OH)4, forcing the diatoms into cellular stasis.
• Algivorous Predation: Otocinclus catfish and Neocaridina shrimp are prolific consumers of diatoms, grazing continuously on the soft biofilm.

Prophylactic Measures

1. Substrate Preparation: Thoroughly rinse all new silica-based sands and gravels prior to introduction to remove fine, highly soluble silicate dust.
2. Reverse Osmosis (RO) Water: Utilize RO/DI water for filling and top-offs to eliminate municipal silicate additives, reconstituting it with pure mineral salts like Equilibrium (dissolved).
3. Patience and Maturation: Accept diatoms as a natural successional phase in tank ecology; as silicates are exhausted and competitive microbial biofilms mature, the diatom population will spontaneously collapse.