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!

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.


How do you set up a saltwater aquarium?

Every now and again I try to sneak in a non work-related blog post for our website and social media pages.  Since my family and I just moved into a new house, I thought I would discuss the proper ways to set up a saltwater aquarium.  I just did this last week with both my reef tank (which I was able to break down and set up again in a single day) and my large fish-only system (which I detail below).

I took apart and drained my large saltwater fish-only system about a week before we moved.  The tank is close to 200 gallons, and I was fortunate to be able to take the fish to a local fish store for safe keeping during the move and subsequent set up process.  Upon moving into our new home, I went to work getting it set up again.

Once you have the tank and stand in place, the first step is to aquascape the aquarium with your sand, live rock, and dead coral.  You want to ensure the fish have enough hiding places (caves, overhangs, etc) to feel secure, but also enough open swimming space to eat, swim, and be seen by you (why have a fish tank if you can’t watch the fish?).  You also need to make sure the rock and dead coral are securely mounted, so that you don’t have rock slides.  At this point I like to position all the equipment (filters, skimmers, heaters, powerheads and pumps, etc) that will be used to run the system.

Once the tank is aquascaped and the equipment is in place you can fill it with freshwater, ideally from a garden hose.  That’s a lot faster than using buckets or pitchers.  When the tank is filled you can add enough salt mix to bring the salinity to your desired level (I recommend a specific gravity of 1.020 – 1.023 for fish only, and 1.024 – 1.025 for an aquarium housing corals and invertebrates) and turn on your equipment.  You’ll want to make sure you have your salinity and temperature where you want them prior to adding any fish (a good temperature range for most saltwater fish tanks is 77-80 degrees).

At this point you will have a tank full of sand, rock, and water but not fish.  Your temperature and salinity will be at ideal levels, but you’re probably not ready to add fish just yet.  How long your tank remains empty will depend upon what stage your water is in with respect to the nitrogen cycle.  Without boring you with too much science, you will typically see a spike in ammonia (which is lethal to fish and corals) within a few days of setting up the tank.  That toxic ammonia will be converted to somewhat less toxic nitrite, and eventually to relatively harmless nitrate.  The process can take anywhere from 7 to 50 days, and can be sped up with the use of bacterial additives or by seeding the new aquarium with a little sand or live rock from a healthy existing system.

The only way to know where your levels are is to test your water frequently with a good test kit.  Once you see zero ammonia and nitrite, and the resulting spike in nitrate, you’ll be ready to do a large water change (to reduce the nitrate) and begin stocking your aquarium with fish.  Best to stock slowly and start with a few hardy fish (such as damsels or cardinals).  When they are settled and doing well, you can slowly add more fish and eventually invertebrates like corals and shrimp.

It’s difficult to wait to stock your new aquarium, but patience and attentiveness really are the keys to success.  If you have any saltwater fish tank questions, please let me know.  I’m offering free aquarium advice with any new SEM or SEO campaign!