RecifAtHome guide
A reef aquarium is no harder to maintain than any other tank: above all, it takes patience and consistency. This guide takes you step by step through the advice we have given in our shop every day since 2010.
In short
- Aim for 100 to 300 litres to start with: the larger the tank, the more stable the water.
- Use only RO water and a quality reef salt.
- Wait until the cycle is complete (4 to 6 weeks) before adding the first fish.
- Add livestock gradually: clean-up crew, hardy fish, soft corals, then LPS and SPS.
1. Choosing the size and location
For a first reef tank, 100 to 300 litres is the best compromise. A larger water volume makes mistakes less serious: a temperature swing, overfeeding or a missed top-up has far less impact. A nano reef (under 60 litres) is possible, but it is much less forgiving.
Keep the tank away from windows (sunlight encourages algae) and radiators, on a cabinet designed to support its weight: allow about 1.2 kg per litre when filled, including rock. A tank with a sump is more convenient: equipment stays hidden and the total water volume increases.
2. Essential equipment
- A protein skimmer: it removes organic waste before it turns into nitrate and phosphate.
- Circulation pumps: turn the tank volume over 10 to 20 times per hour for soft corals, 20 to 40 times for SPS.
- Reef LED lighting: essential for corals, which obtain part of their energy through photosynthesis.
- A heater to maintain 24 to 26 °C, and sometimes a chiller in summer.
- A reverse osmosis unit: tap water contains nitrate, phosphate, silicate and sometimes copper.
- Salt and a refractometer to set salinity at 35 ppt (specific gravity 1.025 to 1.026).
- An auto top-off that automatically replaces evaporated water with RO water.
- Test kits: at least alkalinity (KH), nitrate and phosphate, then calcium and magnesium.
3. Setting up and the nitrogen cycle
Place the rock (live or artificial) and then the sand, fill with saltwater mixed the day before, and start the pumps, heater and skimmer. Add bacteria to kick-start the cycle.
Over 4 to 6 weeks, bacteria colonise the system: ammonia from organic matter is converted into nitrite, then nitrate. The cycle is complete when ammonia and nitrite stay at zero for several days in a row. A brown diatom film and then some algae are normal at this stage.
Good to know
Run the lights for only a few hours a day during cycling, then increase gradually: this limits algae.
4. First livestock, in the right order
- The clean-up crew (snails, hermit crabs) deals with early algae.
- Two or three hardy fish, preferably captive-bred, chosen from our beginner-friendly species.
- Soft corals and Zoanthus, easy and tolerant.
- After 3 to 6 months, LPS corals; after 6 to 12 months of stable parameters, your first SPS.
Add only a few animals at a time, about two weeks apart: the bacteria need to keep up with the increasing bioload.
5. Routine maintenance
| Frequency | Tasks |
|---|---|
| Daily | Feed, check temperature and pumps |
| Weekly | 10 % water change, clean the glass and skimmer cup, test KH, nitrate and phosphate |
| Monthly | Test calcium and magnesium, clean pumps if needed |
| Every 6 months | Replace RO pre-filters, descale pumps |
6. The most common mistakes
- Rushing: adding fish before the cycle is complete.
- Overfeeding: excess food becomes nitrate, phosphate and algae.
- Using tap water, or topping up with saltwater (only fresh water evaporates).
- Correcting a parameter abruptly: stability matters more than the perfect number.
Frequently asked questions
How long before adding fish?
Wait until the nitrogen cycle is complete, usually 4 to 6 weeks. Ammonia and nitrite must read zero.
What size tank for a first reef aquarium?
Between 100 and 300 litres. Parameters fluctuate too quickly in smaller tanks; larger ones significantly increase the initial cost.
Can I use tap water?
No. It contains nitrate, phosphate, silicate and sometimes metals that feed algae and harm corals. Use RO water.
How many fish in a 200-litre tank?
Four to six small fish (under 8 cm), added gradually and compatible with each other.
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Guide written by the RecifAtHome team, coral aquaculture in Roche-lez-Beaupré (France) since 2010. Updated: October 2026.