Have you ever seen a video on coral reefs, or been lucky enough to experience them while diving or snorkeling and been fascinated by them? Reef keeping is a wonderful hobby that can delight anyone from the casual observer to the die-hard enthusiast.

Corals are marine invertebrates from the phylum cnidaria. They are colonial animals, consisting of individual polyps that form colonies. Corals and jellyfish are actually closely related, both belonging to the cnidarians, an ancient group of animals with stinging tentacles with various degrees of potency. Corals are found in deep waters, temperate waters, shallow tropical waters, and now many aquarium hobbyists’ homes!

Whether you are an aquarium enthusiast or a beginner hobbyist, corals are a great way to brighten up your aquarium, bring a piece of the ocean into your home/office, or simply show off your aquarium-keeping skills. 

Differences & Similarities Between Hard Corals & Soft Corals

Corals consist of genetically identical polyps. A polyp is an individual unit of the structure, one end attaching to the skeleton and the other containing tentacles with nematocysts (stinging cells). 

Hard Corals - Scleractinian/Stony Corals (LPS & SPS) 

Hard corals are made up of hard skeletons composed of calcium carbonate (CaCO3). When they die, their exoskeleton is left behind. 

LPS stands for large polyp stony corals and SPS, small polyp stony corals. Even though these corals have similar names, they have many similarities and differences!

Similarities

• All in the order Scleractinia 
• They both take up calcium from the water to build their skeleton
• They both have soft-bodied tissues containing polyps
• Majority of them contain zooxanthellae - they are photosynthetic

Differences

• LPS corals have large fleshy polyps
• LPS corals generally require a slow and calm water flow 
• LPS corals generally have a strong stinging capacity
• LPS corals are generally easier to care for
• LPS corals are generally more aggressive

• SPS corals have smaller polyps
• Most SPS corals look more ‘stick-like’, but there are exceptions such as Montipora
• SPS corals require relatively stronger flow
• SPS corals have less stinging capacity
• SPS corals are generally more difficult to care for

Soft Corals - Alcyonacea/Ahermatypic Corals (Softies)

Soft corals do not produce the hard calcium carbonate skeletons like hard corals, instead, they have small pieces of calcium carbonate that make up a skeleton in their tissues called sclerites. True soft corals contain 8 radially symmetrical polyps at the end of their tentacles classifying them in the order octocorillians. 

Soft corals are pretty hardy, enabling them to grow well, able to tolerate water fluctuations, and can adapt to different amount of lighting and water flow. 

Coral Fact: Within their polyps, corals, both hard and soft, contain microscopic, single-cell algae called zooxanthellae that under photosynthesis produce energy for their host coral. In turn, the corals provide shelter for the zooxanthellae. This is called a symbiotic relationship. It is these organisms that are expelled during coral bleaching events leaving the coral exposed to light and causing them to turn white. However, not all corals contain zooxanthellae. Those are called NPS or non-photosynthetic corals. NPS corals rely on feeding for their energy uptake.

How To Care For Corals 

As with any aquarium keeping you always want to create a similar environment from which the organism originates. When caring for corals you will want to ensure the water parameters are stable, as corals can be sensitive to changes. 

Having said that, soft corals are the most tolerant of changes in water and excess nutrient, making them an ideal choice for beginner hobbyists. You should still aim for stability as it will help you succeed in the future when you want to keep other types of demanding corals.

LPS corals also quite tolerant of changes in water and excess nutrient, but they require calcium and alkalinity supplement to build their skeleton. 

SPS corals are more demanding when it comes to water conditions. Nitrates should be under 20ppm and phosphates should be less than 0.1. They require both strong water flow and lighting to thrive, and will not tolerate any aggressive neighbors. Most importantly, SPS requires a very stable environment to thrive.

Ideal Water Conditions

Tank Set-Up

You will want to start with a reef tank that is large enough for your corals. Note that some corals can grow up to 5-6in a year, while others are much slower growers. So depending on which types of corals to keep, it will be a main factor in determining your tank size.

A larger tank can provide more room for error, as a larger body of water is more forgiving with parameter swings. As you could imagine, a drop of solution in a 20-gallon tank is more concentrated than it would be in a 180-gallon tank. We always recommend to our customers to go as big as it is feasibly possible.

What powers a reef tank? 

A reef tank is an aquarium that employs live rock for biological filtration, strong lighting for coral photosynthesis, power heads for flow, a protein skimmer for waste removal, and some form of nutrient remover, all working together designed to achieve the parameters stated above for an optimum environment to support coral growth.

Live Rock

In a reef tank, live rock is at the heart of your biological filtration system. It provides surface areas for bacteria to live. You should aim for rock with various shapes and sizes with lots of voids and porosity, and as much as possible but with room for fish to swim and corals to grow.

Lighting

Lighting is crucial for a majority of corals in the hobby as they are mostly photosynthetic. SPS corals require strong lighting, whereas LPS and soft corals can work under a wide range of lighting conditions depending on the species. You have many choices for lighting technologies. A decade ago, the best lighting option would be metal halide or T5. In this day and age, as LED technology has matured, LED lighting is now the preferred choice over other types of lighting. Here at Piece of the Ocean, we use 100% LED lighting to grow all of our corals.

Power heads

Water flow is vital for corals, as they are stationary. It provides them with fresh oxygen, enhances photosynthesis and respiration, flushes out waste, transports offspring, and allows corals to catch prey. Poor water flow can cause many problems for your corals, including slow tissue necrosis (STN) and undesired algae and bacterial bloom that can overwhelm and kill corals. The strength of flow requirement differs between soft and hard corals, but ideally all water flow should be random and indirect. 

Protein Skimmers

A protein skimmer is considered a must-have in a reef tank, especially for beginners. While there are those that succeed in keeping a reef tank without a skimmer, those tanks have achieved a balance in nutrient uptake and export, and are not recommended for beginners. A skimmer works by mixing air with water to create fine bubbles that bind to organic waste, and as a result removing it from your water before it further breaks down into phosphate and nitrate.

Nutrient Remover (Phosphate and Nitrate)

Nutrient removers or a nutrient sink, are methods employed to remove phosphate and nitrate. The most commonly used methods are a phosphate reactor using some type of phosphate remover media such as granular ferric oxide (GFO).

Nitrate is removed by anaerobic bacteria - bacteria that grow in spaces with low to no oxygen within your live rock, a deep sand bed, or other low oxygen areas of your tank. The process of reducing nitrate in the aquarium with anaerobic bacteria is often referred to as denitrification or a method called Natural Nitrate Reduction.

Refugium

A refugium where marine plant such as chaetomorpha can grow without being disturbed by fish also helps reduce nitrate and phosphate. We prefer this way as it is more natural and allow levels to balance out very gently to the tank's needs

Diet & Feeding

Most corals will get sufficient nutrients from lighting in the aquarium, but they can benefit from feeding. If you choose to feed your corals, do so with a variety of foods a few times a week.

You will also want to feed corals depending on their type. Mixed corals do better with liquid or powder form, and LPS corals either pellet or powder formed food. When feeding corals it is important to reduce the water flow so the corals can easily catch prey. 

You can feed your corals additional nutrients. Adding amino acids with SPS corals encourages tissue growth and enhances colorations - potassium boosts blue coloration, boron for red coloration, and iron for green coloration.

Let’s Talk About Compatibility

Before adding corals to your aquarium, you need to consider the compatibility of corals and other marine organisms co-living together. Some fish may nibble on corals, therefore you need to understand which marine critters are compatible. We understand you may not only want corals so we have put together a small list of compatible, or more commonly known as reef-safe fish and inverts. Please note that the list is a lot longer. This is just to give you a place to start.

Some corals can be aggressive to other corals or produce a nasty chemical toxin that can harm humans, so always be cautious before handling and when feeding. Always research the specific species or ask an aquarium professional if you are unsure.

Can You Mix SPS Corals With LPS Corals?

You can, but placement is crucial so you must plan accordingly! Generally SPS corals must go at the top to receive stronger lighting and LPS prefer a dimmer location at the bottom. 

As mentioned, SPS corals do not deal well with aggression and due to their specific requirements with feeding, light, water flow, and nutrient level, it is best to keep them separate from each other. There are tanks dedicated to just SPS for this reason. 

What LPS & SPS Corals Are Beginner Friendly?

It may be your first time owning these beautiful creatures, and trust me there are so many online that it can be tempting to pick the prettiest or largest without even thinking about how hard they are to look after! 

There is nothing worse than spending hundreds of dollars on a coral and within a few weeks, the coral died due to it being for experts. Beginner corals are still beautiful and come in all shapes, sizes, and colors - to help you out we have put together a list of beginner corals we recommend!

Beginner Soft Corals

• Mushroom Corals
• Star Polyps
• Xenia
• Leather Corals
• Zoanthids & Palythoas

Beginner LPS Corals

• Hammers & Frogspawn
• Duncans
• Bubble Corals
• Candy Cane Corals
• Brain Corals

Beginner SPS Corals

• Montipora Capricornis
• Montipora Digitata
• Birdsnest
• Stylophora

To Finish

So there you have it, by now you should have an idea of what you need to know starting to keep LPS, SPS, and soft corals. Always select coral on your abilities, and most importantly have fun because that is what being an aquarium hobbyist is all about!