Working with reef tank hobbyists every day, we get certain questions over and over again. There’s a lot of gear, terminology, and conflicting advice out there, so let’s break down five common reef tank questions reefers call and email us about, along with some helpful tips that can help you make better decisions and avoid mistakes along the way.

Do I NEED a Protein Skimmer?

The short answer is that a protein skimmer is not required to keep a successful saltwater aquarium. But once you see the gunk a skimmer can pull out of the water, it's hard not to run one.

A skimmer works by mixing air and water to create millions of tiny bubbles. Organic waste in the water sticks to those bubbles, rises into a collection cup, and gets removed before it can break down into nitrate and phosphate.

That gives you several benefits:

  • Better nutrient control
  • Improved oxygen exchange
  • Often a higher pH
  • Extra margin for error if you overfeed or miss maintenance
Protein Skimmer Diagram Click to Enlarge
Tank Type / Situation Protein Skimmer Recommended? Why
Small nano reef (<20 gallons) Optional Water changes and light stocking are often enough to maintain water quality.
Lightly stocked aquariums Optional Many successful tanks run skimmer-free with consistent maintenance routines and other simple filtration methods.
Minimalist or low-tech reef setups Optional Some hobbyists rely on other nutrient export methods like a large macroalgae refugium.
Medium to large reef systems Recommended Larger water volumes and bioloads are harder to manage without additional filtration.
Tanks with heavy feeding Recommended Helps remove excess organics before they break down into nitrate and phosphate.
Reefers wanting lower maintenance Recommended Adds a margin for error and can make the tank more forgiving.
Heavily stocked reef tank Strongly Recommended Extra nutrient export helps manage waste from increased feeding and bioload.
SPS-dominated reef Strongly Recommended Stable nutrients and improved oxygen exchange benefit sensitive corals.

Did You Know? Protein skimmers only work in saltwater aquariums. The foam fractionation process that allows organic waste to stick to bubbles depends on the surface tension properties of saltwater.

Which Sand Should I Use and How Much?

Choosing sand for a reef tank comes down to three main factors: dry vs. live sand, grain size, and how much sand you actually need.

Dry Sand vs. Live Sand

Dry Sand
Clean aragonite-based sand with no added bacteria. Dry sand is almost always less expensive than live sand. If you're using live rock or bottled bacteria, dry sand is a good way to save some money and achieve the same end result. Just keep in mind that it can be a little more dusty than wet live sand, so be prepared to give it a rinse before use.

Live Sand (most popular)
Live sand comes packaged wet with beneficial bacteria in the bag. It's a popular choice because this bacteria can help jumpstart the tank's biological filtration system and allow you to add fish more quickly.

Sand Grain Size

Fine sands create a bright, natural appearance and are ideal for sand-sifting fish and invertebrates like gobies, nassarius snails & sand-sifting starfish, but they can blow around in high-flow tanks. Coarser substrates like crushed coral stay put better but tend to trap more detritus.

Most reefkeepers find that a sand with a medium grain size, such as Caribsea Special Grade, is a great middle ground.

One option I generally avoid is black sand. It looks incredible on day one and makes fish and corals pop, but black sand often contains magnetic particles that can get caught in algae scrapers and scratch your glass. It’s also surprisingly difficult to keep looking clean over time.

Saltwater aquarium sand comparison


How Much Sand?

Years ago, deep sand beds were all the rage, but modern reef tanks typically use a shallower sand bed of 1-2", which is easier to maintain long term.

We often use 1 lb of sand per gallon as a starting point, but for a more accurate answer, we have our Sand Bed Calculator where you can enter your tank's dimensions, desired sand bed depth, and which type of sand you're using.

How Can I Get My Tank Ready for Vacation?

Leaving your reef tank unattended can feel stressful, especially if you’ve spent months or years building a stable system. Thankfully, a little preparation goes a long way.

Helpful Automation

A few tools can help improve stability in your tank and reduce your own stress while you're away.

  • Auto Top Off (ATO): This is by far the best automation-related investment you can make. An ATO system uses a sensor to automatically add freshwater to the tank when the water level drops due to evaporation. This helps maintain a stable salinity and is generally a good upgrade for not just vacations, but for everyday reefkeeping.
  • Automatic Feeder: If you don't have a tank sitter, this is another must-have. Just be sure to set it up ahead of time and get your fish used to eating pellet foods if they're not already.
  • Aquarium Controller: Easily monitor your aquarium water parameters remotely and get alerts if something doesn't look right with an aquarium controller like the Neptune System Apex.

Don't Wait Until the Last Minute

Avoid doing major maintenance the night before you leave. It's easy to forget to turn a pump back on or bump a dosing line and not catch it until you return from your trip.

Before Your Trip:

  • Perform a water change
  • Empty and clean the skimmer cup
  • Refill Dosing Containers
  • Set up or refill your automatic feeder
  • Fill your ATO reservoir

Keep Tank-Sitter Instructions Simple

If someone is checking in on your tank, simplicity is key.

Pre-portion food whenever possible and avoid asking a non-hobbyist to troubleshoot complicated issues. The more decisions they have to make, the greater the chance something goes wrong.

It also helps to leave:

  • Emergency contact information
  • Instructions for basic tasks only
  • Contact info for a local reefing friend or service company
  • Backup pump or heater in an easy-to-find location

When Should I Look Into a Calcium Reactor? 

A calcium reactor is one of the most effective ways to maintain calcium and alkalinity in a reef tank, but it’s usually not a solution most hobbyists need.

How a Calcium Reactor Works

A calcium reactor works by pushing aquarium water into a reactor filled with a calcium carbonate media. A small amount of carbon dioxide (CO2) is injected to lower the pH of the water inside. This slightly acidic pH level slowly dissolves the calcium carbonate media, releasing calcium and alkalinity. This concentrated solution slowly drips back into the aquarium or sump.

Calcium reactor setup diagram

Signs Your Reef Tank May Be Ready for a Calcium Reactor

  • Your tank is packed with fast-growing stony corals
  • Alkalinity and calcium demands continue increasing
  • You're noticing a sizable salinity increase with large volumes of two-part dosing
  • You like tech and trying out new gear

For heavily stocked reef tanks, calcium reactors are often one of the most efficient and cost-effective supplementation methods available over the long term. That said, the initial setup cost is higher than a standard two-part dosing system since you’ll also need supporting equipment like a CO2 tank, regulator, feed pump, and pH monitoring equipment.

Confused about dosing? Learn More: What is Dosing a Saltwater Tank?

What Is a TDS Meter and What Is It Actually Reading? 

If you use RO/DI water for your reef tank, a TDS meter is a must-have tool. TDS stands for Total Dissolved Solids. A TDS meter measures the electrical conductivity of water and estimates how many dissolved ions are present, displaying the result in parts per million (ppm).

In other words, it's an indicator for water quality. In the saltwater hobby, we aim to use 0 TDS water for salt mixing and top offs.

Most Helpful Places to Measure TDS

RO/DI system diagram with TDS meter

Water entering your RO system
This will tell you the starting TDS of the water entering your RO/DI system. Compare this TDS reading to the TDS leaving your RO membrane and you can easily calculate rejection rate and determine how well the membrane is performing.

Water exiting your RO membrane
This reading is typically in the single digits, but will depend on the quality of tap water you're filtering. RO membranes can reduce TDS by up to 99% under ideal conditions.

Water exiting your DI stage(s)
This is arguably the most important reading as it's the TDS of your final filtered product water you'll use in your aquarium. We always aim for 0 TDS.

Limitations of a TDS Meter

They don’t identify specific contaminants
A TDS meter only measures the total amount of dissolved ions in the water, not what those ions actually are.

Not All Contaminants Will Register as TDS
A TDS meter only measures the conductivity of the water. Things like organics, chloramines, or other non-conductive materials won't affect TDS readings, so it's important to maintain your pre-filters, even if your filtered water is showing 0 TDS.

In-Line vs. Handheld TDS Meters

Inline TDS Meter (preferred) Handheld TDS Meter
Permanently installed on the RO/DI system Portable and easy to use anywhere
Monitors water in real time as it’s produced Great for testing storage containers and mixing bins
Eliminates many outside variables Readings can be affected by containers or contamination
Best for daily monitoring of filter performance Best for occasional spot-checks