15 Steps to Starting a Saltwater Aquarium: The Lasse Method

Display Tank.

Photos are all courtesy of Lasse Forsberg. ©2019, All Rights Reserved.


There are many methods to start a saltwater aquarium--each major aquarium product manufacturer has its own. Common to most, however, is that they focus on keeping difficult and demanding corals--especially SPS. Are you looking for a method-specific SPS aquarium? If yes, then maybe you should choose a method from one of that group of manufacturers. But if you just want to start a saltwater aquarium for fishes, invertebrates, soft corals, most LPS, and many non-demanding SPS, then my method might not be so bad. At least it has not been for me in my forty years of reef-keeping.

Below is the method I have worked out over the years:


1) Get the appropriate size aquarium 25 liters or larger. For smaller aquariums, look for those that have the sump built into the back, also known as “All in One” (AIO.) It’s an excellent starter aquarium.

2) Decorate the aquarium with rock and sand. Use dry or live sand. You may add some sand from an existing aquarium. The rock can be both alive and dead/dry. It can be good to have a 50 – 50 mix of live and dry. I never clean the rocks, I just rinse them off.

If I use live rock (LR), I try to pick from as many stores as possible, always looking for "fresh" rock. I want as many and as different hitchhikers as possible. About 90% of the hitchhikers are beneficial, and about 10% can be harmful (depending on which ones). If I get a “bad guy,” then I deal with that later on.

If you do not have access to live sand, used filter media, or some old water. There is a pretty good product available in order to avoid water that is too “sterile” in the beginning: Tetra Bactozym.

3) Fill aquarium with water and salt and mix up to about 34.6 parts per thousand (PPT) salinity.

4) Put in and start your equipment (return pumps, power heads, protein skimmer, if used, foam filters--if you chose that--and heaters.) Wait with active carbon, granular ferric oxide, and similar equipment. Let the water circulate for one or two days.

5) Introduce a healthy, well fed, lively fish that is not shy.

In a large aquarium start with 2 - 3 fish. The reason for introducing fish as early as this is that you need something that produces ammonium (NH4) in order to get the vital nitrification process to start. In a newly started aquarium, there is no bacteria-related production of ammonium and the production of ammonium from the fish(es) is controlled by how you feed the fish. With this method, you will have full control over the NH4 production the first few weeks.

An orange-spotted sleeper/sifter goby, Valenciennea puellaris.

Photos are all courtesy of Lasse Forsberg. ©2019, All Rights Reserved.

6) Add some nitrifying bacteria every day for three weeks or inoculate with detritus from an already functioning aquarium every day. There are many special bacterial strains available to buy, including a mixture of nitrification and break-down bacteria--avoid them in the beginning--only the nitrifying bacteria are of interest. I normally use a freshwater product--Sera NitriVeck--and dose 20 ml per 100 liters/day. Do you have an old aquarium running? Then take and turn out the filter in a few liters of water--fresh or salt--does not matter. Put it in the refrigerator, and then pour in an appropriate amount every day into your new aquarium. At the start of an aquarium it can be a good method to use an internal foam filter, which helps the nitrification to start. It can later be removed if you want.

7) Feed extremely sparingly at the beginning. I usually only use frozen large brine shrimp for the first 3 weeks and only give three to four shrimp per fish. The first week I feed every third day (this small amount) and the second week every other day (the same small amount) and the third week, every day (the same small amount). On Week 4, I start to increase the amount.

8) Run a full lighting duration right from the start if you plan to follow step 9. otherwise - start 3-4 day before the introduction of CUC. If using LED, do not have too high intensity, but the full duration. The reason is, after all, to start algae and other things so that they begin producing. They get phosphorus because the rock is not carefully cleaned and from the frozen brine shrimp. Nitrogen is also necessary in the beginning--see later.

9) Introduce the Clean Up Crew (CUC) around days 3 - 4 and as many different species of snails and hermits you can find. Preferably a dozen snails and as many hermits (small) per hundred liters and at least the number if the aquarium is below 50 liters. See if you can find at least one sea urchin - the long spine black urchins are usually the best. Avoid very small ones. Crabs (emerald and sally lightfoot) are a good complement as well. Shrimp, especially the coral banded shrimp, Stenopus hispidus, is good in the beginning because they hold down bristle worms--not eradicate them but keep the population down. The reason why the CUC should be added early is that they must prevent the microalgae from building up a too-large biomass and thus a too-high daily production of microalgae. Not cleaning the live rock too much gives some food to the CUC in the introduction phase.

A red variant of Scooter Blenny, Synchiropus ocellatus.

Photos are all courtesy of Lasse Forsberg. ©2019, All Rights Reserved.

10) Add some nitrates around day 5--just a few ppm. Get potassium or sodium nitrate. Add 40 grams to 460 grams of water. Dissolve 1 ml of this solution per 100 liters of water. This solution raises NO3 by about 0.5 ppm. Target: about 3 ppm.

11) Introduce the first soft corals or mushrooms after about one week. Hardy LPS corals can come some weeks later. Most corals are consumers--not producers—and they do not affect the bio-load of the system--it's just the opposite. However, non-photosynthetic corals should be avoided for the moment. In connection with the introduction of corals, it is time to start increasing the intensity of the light if possible.

12) If you get a small brownish color on the sand, then try to stir the sand a couple of times every day with a small stick or an EHEIM gripper.

13) Change water at the earliest after about 4 weeks. Introduce new fish slowly and patiently. Do not increase the feeding too fast, just slowly and carefully.

14) Do not test water parameters. Wait until the aquarium is a few months old or you have a lot of hard corals. Once the aquarium has established itself for a few months you can start testing if you want to. The most important thing to test is calcium and alkalinity if you have hard corals. Now it is also time to start--if you want— start testing and change the values of inorganic nutrients like PO4 and NO3 with one or another method.

15) After about 4 - 8 weeks, it’s also time to start some other stuff if you like, a refugium for example. Also, look at a small thing called an Oxidator--something I use to get a clear water without yellowing--but wait about 2 months.

Of course, there is some real thought behind my method: nitrification and other biological life should get started as soon as it possible and the risk of ammonium formation (and thus free ammonia) is removed. But the production of micro-algae should also get started as soon as possible, and that’s why you need "harvesters"--that is the CUC.

With these guidelines, I have started hundreds of aquariums without any algal problems in the beginning.

After the first three to four weeks, it is usually a good idea to change water every week, between 10 - 20% if you want to go that path.

Plectranthias inermis

Photos are all courtesy of Lasse Forsberg. ©2019, All Rights Reserved.


Once the aquarium is stabilized after about 4-8 weeks, you can start introducing new fish at a slow pace. Never increase the feeding suddenly.


The idea of not testing water parameters during start up may seem very provocative, but in my experience--since there are a lot of myths about target values for different inorganic nutrients all around--there will often be overreactions, especially by beginners. Having high levels of inorganic nutrients (as PO4 and NO3) in the water column does not mean that you will get algae automatically (compared to low and dino/cyanobacteria).

Lack of grazers (CUC)--on the other hand--gives direct algae problems regardless of the nutrient levels in a newly started aquarium. In a tank with well-established corals, they will compete with the algae for the nutrition and the CUC will not be as important. Put your money into a large, diverse, and good CUC at the start instead of a lot of measuring equipment--it is both more fun and more efficient. When you know what you want to do with your aquarium—yes--then you can start manipulating different parameters, but let it run for 2-3 months (at least) beforehand.

With these 15 steps in my head, I have successfully started many aquariums without any algal or other problems in the beginning.

Sincerely Lasse

Edit - Point 6 was not really clear consider what I meant with mixed bacteria strains in the beginning. The sentence is changed now--I do not normally used mixed strains in the beginning

I want to thank @Seawitch and @Bouncingsoul39 for help with the editing of the article.

Sincerely Lasse


Note from the Editor: This article is Lasse Forsberg's method (The Lasse Method) for starting saltwater aquariums, which Lasse was kind enough to share with us. We expect some readers will view parts of this method as controversial. Please note, however, that Lasse has been a reef aquarist for over 40 years and has also worked in fisheries and aquaculture his whole professional life. It's hard to argue with someone who has so much experience under his belt.


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Author Profile: Lasse Forsberg

Lasse Forsberg, is from a little town in Sweden. He has been keeping aquariums for over 40 years, and in his professional life, he has always worked with fisheries, aquaculture, and public aquariums on the technical side.

He is a valuable member of the Reef2Reef forum, and his super interesting build thread may be found here.