Feeding Saltwater Fish

Feeding a saltwater aquarium is more complicated than it seems. If you’re used to feeding freshwater fish where effectively all of them will take almost anything you offer, you will be very surprised at how difficult it can be just to get some saltwater fish to eat at all, let alone to get them to take what you regularly offer the tank.

Pellets vs Frozen

In general, the nutrition in pellets is superior to frozen foods. High-quality pellets such as New Life Spectrum provide complete and balance nutrition using ingredients that all types of fish and even many corals can digest. And because they do that in every bite, you don’t really need any variety.

new life spectrum fish food

The problem with pellets is that if they float, they just quickly go down the overflow, and if they sink, they just get pushed along the sand by the flow until they get pushed under the edge of the rocks. If they get pushed under the rocks, they just feed bristleworms. A few bristleworms on their own are okay, they are great scavengers. But if you are feeding them directly with pellets that get pushed under the rocks, you will quickly have a bristleworm farm instead of a reef tank.

Every single time I’ve had a customer come into the shop complaining of crazy amounts of bristleworms, I ask if they feed pellets and the answer is always yes. It means a lot of that food is getting pushed under the rocks.

How to feed corals
Symphyllia Normally

The only way I would feed pellets is if you are feeding them by hand (not with an automatic feeder) and are actually watching the fish eat them. This means dropping in a few pellets, watching the fish eat them before they even hit the bottom, feeding a little more, and repeating until more than one or two hit the bottom without being eaten. This way you know the pellets you are feeding are actually feeding the fish and not the bristleworms.

Another issue with pellets is that since the vast majority of saltwater fish are wild-caught, many are very reluctant to convert to pellets. Although still unnatural to them, frozen foods are much closer to a natural food that the fish are used to and recognize as food. If pellets are fed, you almost always still need to feed frozen for any fish in the tank that aren’t feeding on pellets yet. If you feed both, always feed the pellets first. This fills the fish that will eat pellets, gets the other fish to associate the pellets with food since their frozen food always comes next, and if they’re hungry enough they may even just try the pellets which helps convert them.

Best foods for corals
Symphylia Eating New Life Spectrum Pellets

The only time I use pellets is to hand-feed certain corals such as Rhodactis mushrooms and most LPS which will actually take 3mm New Life Spectrum pellets. In fact, I had a Symphyllia that never opened up for anything, no matter what I fed, until I hand fed it some pellets. Instantly, the feeding tentacles opened up and it was eating them as fast as it could, I couldn’t believe it. Most corals are more than happy to eat frozen foods though.

Frozen Food

Because of all this, I prefer to feed frozen foods to a reef tank.

One big benefit to frozen is that it stays suspended in the water column instead of floating or sinking. This keeps it where fish will notice it much longer, as well as within reach of corals.

The only downside to frozen foods is that no one food is complete and balanced nutrition so you need to provide variety. And two or three foods is not variety. When I had my system at home running, I was rotating through about a dozen different foods. This sounds like it’s more expensive, but it’s not at all. If you go through a pack of cubes every month, then you either go through all of one pack or a little of each of twelve packs. It’s still one pack per month.

The other benefit of having so much variety on hand is that no matter what fish you have and no matter how picky they are, you have something each will eat. If you usually only have two or three foods on hand, not only are you routinely not providing truly complete and balanced nutrition, but you will have more problems providing something each fish will eat.

Premium Mixes

Best LRS Frozen Fish Food

There are some great frozen food mixes that come as a pre-mixed variety of great frozen foods. Examples are Rod’s Food and LRS. These are great foods, however, they should not be fed until you have a variety of livestock that will eat all of the ingredients in them. If not, it’s the same as buying a pack of mysis or oyster eggs even though you have nothing in your tank that eats either of those, they’re just going to pollute the tank. So don’t hesitate to try these, but wait until you have your tank stocked with a wide variety of feeders and make sure to get the right mix to fit what you actually have in the tank.

Cubes or Flats

How to feed saltwater aquarium fish

Frozen foods are available in two main categories: cubes and flats. The flats are cheaper per weight, but the cubes are a lot more convenient and make it a lot easier to consistently feed the same amount. Also, since you pop each cube out of the foil individually, the other cubes are better preserved and don’t get freezer burn, so they last longer. A flat pack starts getting freezer burn pretty quickly and if you don’t feed the whole pack in a timely manner, you could lose a significant amount of nutrition to freezer burn.

I strongly recommend you stick with the cubes for the consistency if nothing else. If you get to the point where you are feeding so much that the price difference really makes it worth it, then switch over to the flats then.

Nutritional Values: Water Content

I generally don’t get caught up on exact protein, fat, etc. I want a variety and they all have their part. That said, there is one thing that is critical to note when it comes to frozen foods and that is that some list their nutritional values in total, including the moisture content, while others list it based on the DRY weight. This will lead you to look at two brands of the same type of frozen food and have one list the protein at 12% while the other lists it at 70%. At first glance, you’ll never buy another product from that first brand, but when you realize they’re listing the moisture too and that the actual nutrition is usually VERY similar, you’ll know it’s effectively the same.

Amount to Feed

How to feed saltwater fish

I tend to feed heavier than most. I want to make sure the fish have enough to eat and be happy. I’ve found that a lot of people who focus on controlling food input as a way of controlling algae are looking too much at only one of MANY factors that help control algae. You can feed well and have good mechanical filtration that gets the extra food back out of the system immediately, so it’s not a problem. In addition, with protein skimmers, strongly lit refugiums, and even carbon dosing, controlling nutrients to control algae is much more effective now than in the past.

The real problem with controlling food to control algae is that the fish are constantly underfed. The problem with this isn’t obvious right away, but a year or two down the road you see tangs and other fish that are thinner and haven’t grown much, you also have more random, unexplained deaths. By constantly feeding not quite enough, the fish die of malnutrition very slowly, over many months or even years. This long time period leads the aquarist to think it’s not anything they’d been doing that whole time but rather some recent event that’s really just coincidental.

By feeding well and then focusing on getting the extra food out and other methods of nutrient control, you can have a tank where the fish and corals are well-fed and truly thrive long term while still not having a constant battle with algae. Nutrient control isn’t about limiting the nutrients going into the tank, it’s about balancing that nutrient input with nutrient export. Most of the most impressive tanks I’ve seen and worked with were actually fed a lot, but the system could handle it. There was a lot of livestock eating the food and effective export measures to handle what they didn’t eat and the subsequent waste after digestion…

It’s important to understand that when you’re feeding a reef tank, you aren’t feeding the fish and some corals, you’re feeding the tank. The tank as a whole, the whole system, is what you are feeding. Food is going to fish, it’s going to corals, it’s going to the mechanical filtration, some is rotting and the nutrients released from that go on to feed corals, macroalgae in the refugium, and pest algae in the display.

This can help explain why it’s actually much harder to feed new tanks that are lightly stocked. A new tank with a couple of fish and two coral frags is actually the hardest to feed because it’s hard to feed enough for those fish to get enough without overfeeding. If you feed just a little, it can spread out very quickly and the fish miss most of it. If you feed enough to really fill them well, then a lot of food ends up in the filter, under the rocks, etc. This is why I like to get as many fish in as possible, as fast as safely possible. This doesn’t mean to throw everything in over the span of just a week or two, but once you start stocking, try to get out of that beginning rut and reach that synergy where you can actually feed a lot and it’s all handled by the tank.

This brings up the issue of stocking. Ideally, you know everything you want to add before you even start. This doesn’t mean you can’t deviate from your plan if you find something you really like later, but you should have a clear plan of what all you want to add and in what order before the first fish goes in. This plan will tell you the order in which to add the fish (generally from least aggressive to most aggressive) and can speed up the stocking process by telling your local fish store what all you want so they can get it in for you. If you have a plan and simply wait to stumble across the fish you want, it could easily take you over a year to stock your tank. If you special order them and let the store know what you want and when, there’s a good chance they can get you the majority of what you want when you want it (there are always exceptions, especially if you want some less common fish).

All that said, it’s hard to give a clear guide about exactly how much to feed since every tank is different. The amount of fish, the type of fish, their current size, individual variation, and other factors all impact how much food the tank can handle. I try to feed so that it takes about five minutes before the fish are done feeding and there isn’t much extra food. In tanks with aggressive eaters, they may eat a proper amount of food in less than a minute. So you need to watch them eat in the beginning until you have a good idea of how much food they need.

You need to watch the fish eat as much as possible. You can learn a lot about the health of the fish and the tank as whole by watching the fish eat. This doesn’t mean you have to sit and stare at the tank every feeding, but if you have a habit of pouring in the food and walking away every feeding, you will inevitably miss a lot of valuable information. Eating is the best sign that new fish are settling in well. If they are eating, they are happy. If they aren’t yet, you need to determine if it’s just because they’re still new and a little skittish, if another fish is being too aggressive at feeding time (this is often impossible to see except during feeding), or something else. This is also the time you are most likely to see the first signs of other problems in the tank such as a fish that is suddenly more aggressive or has stopped eating.

Fish like food soaked in RO the same way we like foods with some salt, it’s the opposite of what they’re used to. This alone can make them more likely to take to frozen foods that much faster. I usually takes water I’m going to feed, that it in some RO water, and just pour it into the tank. If you turn off the pumps, just put the return pump on feeding mode so it stays off for 10 minutes or so. Leaving the powerheads on keeps the food moving so the fish can see it and so the corals can grab it. If you don’t have enough fish to even feed one cube per feeding, just feed what they’ll eat and keep the rest in the refrigerator until the next feeding.

How Often to Feed

Generally, I feed twice daily. This keeps a good amount going in at each feeding without being excessive. I usually fed twice daily and each feeding would have two types of the larger foods and one of the smaller ones. Most of the smaller ones are mainly for the corals, but smaller fish such as anthias, firefish, small gobies, etc. will be happy to eat them too.

Best frozen foods for saltwater fish

You may need to feed more often if you have certain fish such as anthias. They are planktivores that feed on small meaty foods in the water column. This feeding style means they eat a little at a time, but they eat constantly in nature. This is the main reason it can be so hard to get anthias to thrive, even in tanks that get fed a lot, because if all the food is being fed in two big meals instead of a little bit at a time throughout the day, they can’t fill up the way the other fish can. This is one reason why if you are even going to try anthias, they should be the very last fish in the tank so that they only go in once the tank can handle the increased feeding schedule. Even then, it’s easy for aggressive feeders to dominate at feeding time and still leave the anthias with less than they really need. This usually leads to them slowly doing over the course of a year or so even if they settle in well and want to eat. In my opinion, the best option for anthias would be a display tank in a store where people are around all day to do many feedings (at least 4-6x throughout the day).

The other benefit of feeding more often is that when life happens and you miss a feeding, it’s not nearly as much of a problem. If you go out on a Friday night and completely miss the feeding, it’s not the end of the world. If you feed less or less often, that same scenario is very different for the fish.

The big exception to feeding frequently like this is if you have a predator tank. Depending on what all you have, you still may need to feed just as often, but certain fish will eat more qt a time but a lot less often. Moray eels, sharks, and many other fish may fill up on a lot of food just once or twice a week. So adjust feeding according to your actual stocking.

My Favorites

My favorite foods in general order of preference are:


  • Fish eggs
  • Spirulina Brine
  • Mysis
  • Reef Plankton
  • Mega Marine
  • Krill


  • Calanus
  • Baby Brine Shrimp
  • Rotifers
  • Cyclops
  • Coral Gumbo
  • Invertebrate Food

High Algae Foods:

  • Spirulina Brine
  • Emerald Entree
  • Mega Marine Algae

Basically, feed everything your local fish store carries that will be eaten by something in your tank and just rotate through them. The only one I skip is squid because it is pretty large pieces that my fish didn’t seem interested in.