Once you have all the equipment and supplies, it is time to start setting up the tank. Your equipment should include instructions unless you purchased it used, in which case you may need to ask the original owner.  A few things to be aware of:

  • This is not a fast process.  Once the equipment is set up, it will take several days for the water chemistry to stabilize before you should add any fish
  • New aquarists love to feed a lot. Resist the urge. This is the number one cause of failure and people giving up on the hobby

An important note about the following tank starting instructions: The best strategy for reducing algae growth is avoid using your aquarium's light for the first 3 weeks. This allows nutrient to be used first by by bacteria and other microorganisms. Ambient room light is fine.

This guide is for aquariums between 10 and 125 gallons. More live rock at each step should be considered for larger aquariums.

Day 1: Filling up

  • Fill the tank with conditioned or pure water and turn on your filters, skimmer, and powerheads to get water moving
  • If you do not have a carbon/charcoal satchel or pad which came with your filter, You can buy a premade carbon satchel or a filter bag and fill it with aquarium carbon (baseball size amount is good) to absorb any weird toxins which may be in the water. This can go anywhere there is water flowing, ideally in a filter where there is space. Make sure this does not block flow and cause overflow. 
  • Mix in the salt needed to bring the water up to .020 parts per thousand (the bottom range of the good zone on your hydrometer/refractometer/salt meter
    • you want to under do it at first, you can always add a bit more salt later. Over-doing it and needing to lowering salt concentration after involves dumping salt water and wasting money.

Day 2: Making the water survivable and beginning the nitrogen cycle

  • After mixing over night test salinity and add a bit of salt if necessary
  • Prepare your sand/gravel by rinsing the heck out of it
    • Turn off filters and powerheads and dump each rinsed sand batch into tank. The water will inevitably be a bit cloudy, this will pass.
    • best if done by filling 5 gallon bucket half way with sand then rinsing in batches.
    • if you buy "live sand" you need not rinse it however read here why we do not recommend using live sand initially.
    • Add a .5-1 lb piece of cured live rock to the tank once salinity is between .020 and .024 ppt. This will begin the aquarium cycle by adding a small amount of bacteria, micro-organisms, and nutrient.

Day 5:   Ramping up the cycle

  • Now you can add cleaned aquarium decorations or a few more pounds of live rock. Remember the key is to build up biology slowly...no 10" puffers or dying smelly sponges on new live rock.
    • You may choose to add a first fish ( see acclimation guide). You don't have to...the biology can be ramped up by adding more live rock as well. Choose one which you want to keep around because catching a fish later is a pain. Orange clownfish are durable, cheap, and friendly. Blue yellow-tailed damsel fish are another good option. Chromis are fragile for this stage. If you are going to be having more aggressive fish, a pufferfish, eel, triggerfish, or grouper should be fine at this point so long as it is small (<2" fish, <14" eel). If you are feeling bold you may try a healthy looking tang or angelfish at a higher risk.  Make sure first fish are eating at the store or ideally that you have quarantined them already yourself( as a new fish person, understanding that your aquarium efforts will likely be a lot less tragic by quarantining fish makes you 97% smarter than most beginners). Do not feed a large amount of food trying to get your first fish to eat in the first days.  This food will rot and you will be set back with potential water quality problems. 
    • monitor ammonia with an ammonia alert badge by seachem or with a test kit daily. If you have the test kits, get a baseline value for pH, KH, nitrate, phosphate, and calcium at this time. If not, try to bring a water sample to the local fish store for testing.

Day 6-20: The waiting game

  • Depending on how ammonia is going, you may choose to add another fish or more live rock. You may also choose to add hermit crabs and other "clean up crew animals" that don't eat algae.
  • If the aquarium cycle is not proceeding well and ammonia is accumulating, a characteristic cloudiness may develop. About .5 ppm is cause for concern. An ammonia binding agent such as prime or amquel may be used to detoxify ammonia temporarily but water changes and fixing the problem. 

Day 21: The last changes

  • Turn on your lights starting at 8 hours a day avg
  • Buy snails at 1 snail per 3 gallons to start. Buy more snails or sea urchins if algae gets too wild.
    • Initially there is often a light brown layer that forms on the rocks and glass. This is a diatom bloom and will clear on it's own as the tank continues to balance out.

A few common mistakes to watch out for:

  • Do NOT turn on the heater outside of the water. It may crack if inserted into to the water. Make sure the heater is properly submerged before turning it on

  • Make sure to prime the filter - If you have a hang on tank type filter, you need to fill up the cartridge area of the filter with water in order for the filter to get suction.

  • Starting the U-tube siphon on an overflow box for a sump filter is pretty complicated and we recommend watching this video before trying it for the first time.

  • And Once again: Do not feed a bunch of food that doesn't get eaten. This will be a major problem. If you do this, use a baster or siphon tube to get the food out. The aquarium initially is very fragile to nutrient and feeding even a little bit too much turns your aquarium into a toilet.