Reef tank image

Can you keep fish in your reef aquarium?

As someone who has made more than his fair share of mistakes in the saltwater reef aquarium hobby, I thought I’d tackle this question in this month’s blog post.

While the short answer is yes, you can keep fish in your reef aquarium, it’s usually not the best idea. Aside from compatibility issues (large angels, butterfly fish, puffers, and triggers will all eat corals and invertebrates with gusto) you can have water quality issues. Fish eat, pee and poop, and in a closed system like an aquarium those waste products build-up very quickly. That in turn drives down water quality, which is bad for your corals. And corals are the whole reason why you set up a reef aquarium in the first place. In the ocean this is never a problem, as there are trillions upon trillions of gallons of water. Ocean reefs have the equivalent of hundreds of water changes per hour, which means pollutants never have the opportunity to build-up. The same cannot be said for our tiny glass and acrylic boxes that we call aquariums.

But let’s say you’re determined to keep fish in your reef tank. After all, who doesn’t love the natural look of fish swimming amongst the corals? So what to do? Provided you have a good-sized reef (50 gallons and up, but bigger is always better), a good protein skimmer and a bunch of healthy live rock, and good maintenance practices (i.e. frequent partial water changes), it can be done. Small fish such as clownfish, chromis, and blennies can all be kept in reef aquariums without adding too much biomass to the system.

Although they will (generally) not eat your corals and inverts, larger fish such as tangs and dwarf angels can cause problems. For starters, they don’t do well in small spaces. You’ll need at least a 4 foot long aquarium (75 gallons and up) to keep these beauties, with 6 feet (125 gallons and up) being a much more appropriately-sized tank. And tangs eat and poop a LOT, which will foul-up your water quality pretty quickly. That can really stress your corals and inverts, so unless you have a big system and you’re really staying on top of your maintenance, I wouldn’t recommend trying to keep larger, more active fish in your dedicated reef aquarium.

If you want to keep a reef aquarium, stick with corals, inverts, and perhaps a few small fish, and your tank will be better and healthier for it. If you want to keep the larger, more active fish mentioned above, a large fish-only tank is the way to go.

I hope this advice helps, and good luck with your reef tank!


Keeping saltwater angelfish in the same aquarium

I’m a HUGE fan of saltwater fish, and I have a 180 gallon saltwater FOWLR (Fish Only With Live Rock) aquarium in my living room. By far my favorite type of fish are saltwater angels, as they are among the most colorful and interesting fish available in the hobby.

Keeping a single saltwater angelfish requires some advanced husbandry. They need large tanks (6 feet or more in length), good water quality, and a good diet. But keeping more than one in the same tank requires proper planning, consistent effort, and a bit of luck, as saltwater angelfish are territorial.

In my aquarium I have 6 saltwater angels (along with a few other non angelfish). Two of them are of the dwarf variety (meaning they do not grow larger than 3-4 inches) and 4 are of the full-size variety (with full-grown aquarium sizes of around 8-10 inches, larger in the oceans). Specifically, I have a 2 inch dwarf Coral Beauty, a 2 inch dwarf Lemon Peel, a 4 inch Emperor Angel, a 5 inch French Angel, a 5 inch Asfur Angel, and a 6 inch Queen Angel. They get along reasonably well (more on that later) and they are all healthy and eating well. So how did I do it?

First things first. You need a big tank with good filtration. If you’re going to attempt to keep multiple full-sized saltwater angelfish in the same aquarium, I would suggest a 180 gallon tank at a minimum. You’d be surprised how big, fast, and aggressive these guys can get. A 180 gallon tank might seem huge, but once you see a few angels swimming around in there, you’ll quickly realize it’s not as big as you think. You’ll also need to keep the water quality high, which means you’ll need a good quality filter (I use a large canister filter located beneath the aquarium) and a powerful and efficient protein skimmer to remove waste in between water changes. Speaking of those water changes, I change out 10% of the water every 3 weeks without fail, and you should do the same. There is no substitute for water changes.

Due to their territorial nature, angels need a lot of hiding places. My aquarium has about 100 pounds of live rock arranged in such a way that there are numerous deep caves for the fish to swim through and hide in. That really helps with aggression. Along with the live rock I utilize a 1 inch deep live sandbed to help aid in biological filtration and waste-processing. I feed my fish 3 times each day, including a high quality pellet food, various types of frozen foods, and dried seaweed (Nori). A balanced diet and good water quality are keys to successful fish keeping.

Lastly, stocking order is very important if you’re going to keep more than one saltwater angelfish. All of my fish spend a minimum of 3-4 weeks in quarantine before going into the main display, which helps with disease prevention. Always put your smallest and least aggressive angels into the main display first (this is where research comes in) and allow them to establish their territories before adding larger and more aggressive angels. In my case, my small juvenile Emperor was the first angel added post-quarantine, followed by the small juvenile French angel. Next came my medium Asfur angel, followed by my larger and more antagonistic adult Queen angel. I actually had to remove the Queen angel after a day or two because she was picking on the French angel. She went back to the quarantine tank for a few weeks before being introduced into the main display again, and this time things went a lot smoother.

Keeping large angelfish together isn’t easy, but with proper planning, religious aquarium maintenance and a bit of luck it is very possible. Your reward will be a stunning aquarium with color and activity you could never have dreamed of. Want proof? The photo in this blog post is from my living room tank, and it doesn’t do it justice.

Danny's Purple Tang

The myth of perfect water quality

I’ve spent a lot of time involved in the saltwater fish and coral hobby.  I’ve owned an aquarium maintenance and design company, I’ve been a volunteer SCUBA diver at a public aquarium, and I’ve personally kept saltwater aquariums for the past 15 years.  In that time I’ve fielded a lot of questions from friends and family about all-things saltwater fish, and one of the main questions I’ve been asked is “How do I achieve perfect water quality”.  The answer is, you don’t…

Perfect water quality is a myth.  It doesn’t exist.  Not in the world’s oceans, and certainly not in the small glass and acrylic boxes we keep in our homes.  No matter how often you perform partial water changes, and no matter how good your filtration is, you will never achieve perfect water quality.  There will always be dissolved organic compounds and nitrates in your water, but that’s OK.  Your fish and corals do not require perfection, but they do require clean, stable water.  So rather than focusing on something you can never attain, let’s focus on what you can accomplish.

Clean, healthy aquarium water starts with a properly set-up tank.  The tank should be as large as you can afford and accommodate.  Ideally the aquarium should be “long” rather than “tall”, and it should have a lot of water movement.  The surface of the water should be moving vigorously, which promotes gas exchange and facilitates nutrient and waste export (often called filtration).  While it is possible to keep saltwater fish and corals without the use of a protein skimmer, I would not recommend it.  A protein skimmer is the single best filtration system available, and should be included in any saltwater system set-up.  Lastly, the use of porous rock (preferable live rock) and sand is heavily recommended, as these provide a great deal of surface area for beneficial bacteria to grow upon and thrive.

Once you have your aquarium properly set-up and stocked, you’ll need to maintain it.  The single most important thing you can do for your fish and corals is the partial water change.  Partial water changes are exactly what they sound like.  You’re removing a certain amount of water from the tank and replacing it with freshly mixed saltwater.  In doing so, you dilute the toxins and pollution in your aquarium, and you import fresh trace elements (iodine, calcium, magnesium, etc) that the fish and invertebrates require for proper growth and health.  There’s no on-size-fits-all approach to water changes, but I would recommend at least a 10% water change every 2-3 weeks.  15-20% is better, especially if your tank is smaller or more densely stocked with fish.  The larger the aquarium and the less densely it is stocked, the longer you can go between water changes.  But even with the largest aquariums (200+ gallons) I would never recommend that you go more than 3-4 weeks between water changes.

The other aspect of water quality that you’ll want to focus on is what you are putting into your aquarium.  By that I mean the foods you are feeding your fish, corals, and invertebrates.  In a closed system, fish and invertebrates live in the same water that they export their waste into, so in addition to frequent partial water changes you’ll want to minimize the amount of uneaten food that breaks down in the water column.  A varied diet is important, so I would recommend a good quality pellet food for omnivorous fish every day (I use and recommend New Life Spectrum Marine Formula) as well as daily nori sheets.  I typically feed my fish-only tank with some frozen food in the afternoons (large chunks of shrimp and clams on the half shell for the puffers, and frozen Formula 2 and Angel formula for the tangs and angels).  In my reef tank, which houses live corals and invertebrates, I eliminate the frozen food, as it breaks down and degrades water quality much more often.  I would also recommend that you not heavily supplement your reef tank with coral foods.  These tend to pollute the tank very quickly.  If you’re keeping up with your frequent partial water changes and your lighting is high-intensity, your photosynthetic corals should receive the majority of their food automatically.  I use a supplement (Coral Accel) once every two weeks, right after I have completed the partial water change.

Keeping saltwater fish and corals is a lot easier these days than it used to be.  If you set-up your aquarium properly and adhere to a consistent and frequent maintenance program, you too will be able to create and maintain a thriving saltwater ecosystem in your home.