Coming from a background in freshwater aquariums, I remember staring blankly at people when they would talk about saltwater reef systems. Salinity, alkalinity and phosphates, oh my! It seemed like the world of saltwater was prohibitively complex, so I put off building a reef system for years.

But there's really no reason to be intimidated by reef tanks. At their heart, they don't have to be any more complex than a standard freshwater setup. You just need water, filtration, light and livestock.

With that in mind, we'll be kicking off a small series that I like to call "Reef It Simple", focusing on how easy reef aquariums can be, while helping you to make informed decisions as you progress in the hobby.

For this first week, we're going to focus on aquarium chemistry. Before we get started, you should familiarize yourself with the ideal parameters for a reef tank. We'll talk more about how to keep your system inside of those parameters later in this blog post.

  • Specific Gravity: 1.023 - 1.025
  • Temperature: 72 - 78°F
  • pH: 8.1 - 8.4
  • Alkalinity: 8 - 12 dKH
  • Ammonia (NH3): None
  • Nitrite (NO2): None
  • Nitrate (NO3): < 1.0 ppm
  • Phosphate (PO4): < 0.2 ppm
  • Calcium: 400 - 500 ppm
  • Magnesium: 1350 - 1500 ppm
  • Iodine: 0.06- 0.10 ppm
  • Strontium: 8 - 14 ppm

Getting Wet

First thing's first, you're going to need some water. You could choose to buy pre-mixed saltwater from a local fish shop, but for anything larger than a pico tank this is going to get old and expensive very quickly.

The single best piece of advice that I can give any new hobbyist is to invest a little bit of money into an RO/DI system. RO stands for reverse osmosis and DI stands for deionization. Without getting overly technical, RO/DI water is tap water that has everything else taken out of it. Some systems will include a TDS meter for finding out the Total Disolved Solids that remain in water after it has been filtered, but you can also buy a standalone meter to measure this yourself.

It's often said that an RO/DI system is the most boring money that you will spend for your saltwater's setup. But that boredom will certainly save you loads of trouble in the future. Almost without fail, using tap water will end up leading to problems such as algae or even livestock death. While the addition of chlorine and other chemicals makes tap water safe for us to drink, it's not so hot for fish and coral.

Feeling Salty

There are seemingly endless arguments about which brand of salt is best for coral reef aquariums. What I can tell you, both from personal experience and from years of reading these opinions, is that every major brand of reef salt can produce great results.
It's worth noting that reef salt is slightly different from standard marine salt in that it contains major, minor and trace elements that corals need to thrive. Some hobbyists prefer to use standard salt mix and then dose the elements themselves, but we're focusing on simplicity. 
My personal favorite is Coral Pro Salt from Red Sea. But generally speaking what you're looking for in a reef salt is one that checks off a few boxes:
  • Expected parameters are listed on the package.
  • Does not require complex mixing procedures.
  • Harvested or created in a sustainable manner.

I have used a number of salts over the years, all with good degrees of success. But I've found that my corals are happiest and thrive better when I'm using Red Sea Coral Pro salt. Your experiences may (and likely will) vary.

Filtration Foundation

This is the area where saltwater and freshwater really differentiate themselves. Filtration in the freshwater environment relies largely on something like a hang-on-back, canister or sump filter. In the marine environment, almost all of the filtration happens in the cured rock and sand. We'll talk more about how the water moves around the tank in the weeks to come.

For a primer on filtration, make sure to read up on the nitrogen cycle. The Cliff's Notes version is this - waste from fish and food cause ammonia. That ammonia is toxic to fish and corals. You need an established colony of good bacteria to turn that ammonia into nitrates, which are less harmful to the livestock. These bacteria will establish themselves in the rock and sand that you use in your system.

In my setups, I have preferred to buy dry rock and then add an ammonia source in order to cycle the aquarium. I do this because it allows me to better control what gets into my system. However, if you want to have the chance at pleasant surprises (and don't necessarily mind the potentially unpleasant ones) you can opt to purchase a high-quality live rock. Cycling with dry rock is much, much slower but with either live or dry rock you can speed up the process by using a bacterial water treatment. In either case, having 1 to 2 pounds of live rock per gallon of tank volume should provide great filtration results.

In smaller tanks, it's common to use a hang-on-back filter to give you a contained area for chemical and mechanical filtration. In larger setups you will often see a sump (a smaller tank, with divided areas) used for added filtration. Generally speaking, if you're below 40 gallons, you shouldn't have to worry about using a protein skimmer. Your water changes will take care of that mechanical side of things. However, adding a skimmer can help to ensure better water quality regardless of tank size. As the weeks go on, we'll delve in deep with external filtration, but for now we're just focused on the chemistry inside of the tank.

The other important factor in your reef system is the sand bed. While there are arguments for days about bare bottom versus shallow versus deep sand beds, my personal experience has been that running one pound of sand per gallon of tank volume works very well.

And Then...?

You have a tank, you have some saltwater, live rock and live now what? Assuming that your system is well-cycled (you remembered to buy a test kit, right?) it's time to cover the basics of tank maintenance in regard to chemistry.
Look back at that list of parameters at the beginning. If it seems overwhelming, take a deep breath and my assurance that it's not all that hard. Let's break them down:
  • Specific gravity: This is a measure of the amount of salt that's disolved in the water. You'll measure this via a refractometer or a hydrometer. Refractometers are more precise, but they're also more expensive.
  • Temperature: This is an easy one. Buy a really good heater and get a thermometer too.
  • pH: A little trickier. Mixed saltwater should remain fairly stable in this range. You will see differences under lights and in the day versus the night because of temperature differences. You can use additives to keep this where you want it, but most corals and fish are better at an imperfect but constant pH rather than with us chasing a perfect number.
  • Alkalinity: The more stable your pH, the more stable your alkalinity will be. For the most part, you won't see too much fluctuation here as long as your pH is stable. But if you go above or below the range, you can use additives to bring it back into line.
  • Ammonia, Nitrite, Nitrate: Here's the big one. If you have ammonia, fish and coral are not going to be happy. But once your aquarium's cycle is complete, you shouldn't have ammonia that is not broken down into nitrate. If you do have ammonia, you're either feeding too much or you have too many fish in your tank. You can use additives like Seahchem Prime to neutralize the ammonia, but only do so while finding out the source and correcting it. 
  • Calcium, Magnesium, Iodine, Strontium: These are all primarily related to corals, though some invertebrates and other livestock have elemental requirements too. Corals need certain levels of these elements in order to thrive. If you're using a reef salt mix, chances are that you're going to be fine. As you do weekly water changes, you'll also replace the elements that have been used. As you get more corals, you might find that the elements deplete too quickly. In that case you can dose the elements in combination or singularly as needed. 

"But that's still so much to know!"
You're right. It is a lot to know. But the beauty of a well-balanced (and lightly-stocked) reef system is that many of these factors will handle themselves quite well. Weekly 10 percent water changes will keep most of them in check. Making certain that you do water testing prior to a water change will help guide you as to whether you will need to do a larger change (normally to help control nitrates) or perhaps if you need to add elements back to the water (again, only common in more heavily-stocked coral aquariums).

Wrapping Up

The biggest thing to remember is this—nothing good ever comes fast in reef aquariums. Take your time, cycle your rock and sand very well and then be diligent with weekly water changes. The less time that you spend with your hands in the tank, the healthier and happier everything will be.

In the weeks to come we'll cover ways to make things even easier such as dosing pumps, auto-topoff systems and reef automation. But for now, take the plunge and start setting up your first reef. Just take your time, do your research and you'll be well rewarded by having a beautiful, healthy reef to enjoy for years to come.