Dark Start Cycling is a simple method for new tank starts that helps avoid algae, reduces the need for water changes during the start up period, and helps reduce the occurrence of melting plants when plants are later planted.
Initial Setup
- Layer tank bottom with desired substrate, eg., aqua soil, gravel, sand
- Place and arrange any hardscape features as desired, eg., rocks, driftwood
- Fill tank with treated water slowly without disturbing substrate (cover substrate with paper towels while filling)
- Initialize filter, airstone, heater
- Do not turn on light, reduce ambient light
- Do not introduce fish or plants, and there's no need for CO2 injection at this stage
- Start cycling by introducing ammonia either chemically or by adding fish food every couple of days
- The process can be accelerated with commercial products like Fritz Live Nitrifying Bacteria or API Quick Start
- Test water parameters especially for ammonia, nitrite, and nitrate every few days
- Cycle is complete when nitrate is detected via testing, and ammonia and nitrite register 0 ppm (though the cycle may not yet be fully established at first)
Reasons for algae and plants melting using traditional cycling method for a new aquascape
- Algae in the early phase is often caused by excess nutrients in the water column
- Not enough plant mass and beneficial bacteria to hold algae in check
- In a mature setup healthy plant mass and beneficial bacteria reduce algae risk
- Plants planted at startup are much more likely to melt when ammonia levels are high
- Ammonia spikes are common in the initial phase while the nitrogen cycle is getting established
- Aqua soil substrate leaches ammonia during initial phase
- Aqua soil is rich in nutrients and has a high ion-exchange capacity (called "active substrate" for that reason)
- Conditions in the aqua soil substrate can become quite acidic initially, and plants react with melting
- Additionally, with aqua soil, an initial overload of nutrients can be released in the water column, which triggers algae
- Controlling algae and plant melt when using traditional cycling method involves frequent water changes
- Week 1 -- 25% water change every day
- Week 2 -- 25% water change every second day
- Week 3 -- 25% water change every third day
- Week 4 onward -- 25% water change once per week
Advantages of Dark Start Method
- Dark Start eliminates the need for most of the daily water changes required for new tank starts
- Dark Start is an easy way to pre-cycle your substrate and filter media, and provides stable water parameters for plants and fish from the beginning
- Simply let your aquarium run with substrate, hardscape, filter, and aeration but without light or CO2
- This method works well for driftwood, allowing the wood to leach tannins and reduce the sliming fungus (clean any off after 4 weeks before adding plants)
- After 1 week, do 25% water change
- After 2 weeks, do 25% water change
- After 3 weeks, do 25% water change
- 24 hours later test for ammonia, nitrites, nitrates, pH, if ammonia and nitrite readings are zero, and some nitrates register (ideally 20 to 40 ppm), the cycling is complete and the aquarium is almost ready for planting
- Note: The length of time required for getting the nitrogen cycle going well may vary, so test water parameters thoroughly before proceeding
- After 4 weeks or so, drain tank, add plants, fill with water
- Introduce CO2 after plants are planted
- Introduce fish and other inhabitants gradually, allowing bacteria colonies to grow according to the biomass
The Disadvantage of the Dark Start Method is having to wait patiently for the aquarium to mature without being able to enjoy it.