Should you feed Phytoplankton?

Added: 2026-05-31

[00:00:00]What is up you guys? Welcome back to Tidal Gardens. This video is all about phytolankton and whether or not you should consider feeding it in your reef systems. If you want the short answer is it really depends on your system. But if you want a deeper dive, stick around.

[00:00:17]Let's talk about it.

[00:00:21]Phytolankton is a really high nutrition food source and in nature it forms the primary layer of the food web. So you have this massive photosynthetic layer of phytolankton that the zup plankton eats that eventually your fish and coral eats and it goes up the chain of predators and the highest amount of energy and nutrition comes from that main base layer.

[00:00:52]I've kind of thrown all sorts of phytolankton in the same bracket, but there is a ton of variation in that world here. There's three that we've chosen for their nutritional profiles, specifically for our sea urchin program.

[00:01:07]Now, I understand there are basically none of you out there doing this, but the lessons that informed my choice on phytolankton will likely translate to most aquarium settings as well.

[00:01:20]We, as hobbyists, try to make the most natural reef tanks imaginable and to try to mimic the ocean. But the reality of the situation is our tanks are not the ocean. In fact, they're pretty far apart from what goes on in the reefs. We kind of fake it and we skip a lot of steps.

[00:01:39]And it's entirely possible to skip a lot of steps. I'm going to guess that many of you, like myself, have never really fed phytolanton reef and it probably turned out okay. But if you do want to experiment with this, here's one practical tip. You want to dose it in small amounts and perhaps a couple of times per day rather than one single giant dose because this stuff does clear up pretty quickly all things considered.

[00:02:05]And if you're dumping the entire day budget all at once, you're basically feeding your protein skimmer, not so much your tank.

[00:02:15]Let's get into some nutrition topics.

[00:02:17]The main phytolankton that we like to feed here is called T isocrisis. It is special in the aquaculture world because it is both the perfect size for a ton of things that you're trying to feed. It's roughly three to five microns in size.

[00:02:34]But the one really special thing about it is that it's very high in something called doohexaninoic acid or DHA for short. Doexoninoic acid. It is critical for cell membrane structure and integrity. It is a part of neural tissue and fish and it is really really important for laral survival. Marine organisms can't synthesize DHA. It has to be fed to them. Tea is crisis is one of the most nutritionally dense sources of DHA.

[00:03:12]There was a study back in 1999 by Southgate and Kavanaaugh. They tested the health of damsels.

[00:03:21]They fed damsel fish artmia that was gut- loed. And these fish had a much higher survival rate than ones that did not. Those other ones only had what was called an EPA diet. EPA standing for Ecosapentinoic acid. Let's talk about EPA for just a sec. I would call this the stress recovery and tissue repair fatty acid. You can kind of look at it where DHA supports structures like the membranes and whatnot, whereas EPA is all about signaling. You really want both DHA sources and EPA sources. The gold standard source for EPA is a datom called keto calcatrans. Because ketocorus is a datom, it also uptakes silicut. And there are a few things in your system that really requires silicate. We will get into that in a little bit. But ketocerus is an EPA monster.

[00:04:27]The third major phytolanton that we culture is rotoonus. It's this maroon red phytolanton. What gives it that red coloration is a pigment called ficothine.

[00:04:39]Ficoerthine is special because it imparts coloration to a lot of things that eat it. However, I have to say that the science behind that is a little imperfect. I would say that it's more in the realm of correlation rather than causation.

[00:04:55]But there's quite enough observation that this stuff does help with color.

[00:05:00]Rotoonus is also special because it has both DHA and EPA.

[00:05:08]Very uncommon for a phytolankton to have both. Obviously not in the monster concentrations of Tiscus and keto. So again they play these complimentary roles. But rodamonus does have a complete fat profile in that regard. And lastly, rodamonus is like the protein shake of these phytolantons. It is up to about 60% dryweight protein. And just the biology of this particular phytolankton makes them very easy for other things to digest.

[00:05:45]So hopefully that gives you guys an overview of the three major phytolanin that we feed. They are very complimentary in nature where one might be lower in a certain fatty acid and the other one picks up the slack. Things like rodamonus inject some additional benefits with the red pigmentation, the high protein content and whatnot.

[00:06:10]All three of these were selected specifically for our urgent breeding program. So they had to be of a certain size. Urchin larve really want to eat stuff that's about 5 micron and smaller.

[00:06:22]So some of the more popular phytolantons on the market either might be too large or they might be the right size but have practically an impenetrable cell wall that is not digestible by my baby urchins. So that's how I arrived on these three.

[00:06:44]This being a coral farm, I was hoping that by feeding my tanks phytolankton that the corals themselves would also consume phytolankton. Unfortunately, with very few exceptions, that is not the case for most corals. Most corals prefer to eat zup plankton. There have been studies where a certain coral will consume something like tisocrisis ganapora for example will absolutely consume it. However, that study also showed that it got practically no nutritional benefit from it because the ganapora was completely unable to digest it. It basically spit it all back out.

[00:07:26]But T is crisis cells were found inside the flesh but none of those healthy fats made the transfer. In order for corals to receive that amount of benefit from phytolankton feeding, it has to go through zup plankton first, which is not the worst thing in the world because your tanks have all these little baby crustaceations, too. And by feeding this ultra nutritious phytolankton, you're turbocharging their nutritional profile for both your fish and corals.

[00:07:56]One benefit though that the corals can receive directly from phytolanton is that phyto also slowly releases dissolved organic compounds. If your tank is already high in dissolved organics, this is probably not a perk for you. But many aquariums are basically nutrient deserts and they have to go through the process of even dosing things like nitrate and phosphate or they maintain a certain fish load so that the fish can provide some dissolved organics. If you find yourself in that boat, phytolankton might be one of the best sources of those dissolved organics and that would allow you to have a lower fish load or be more selective about your fish. You don't need a school of green chromas, for example, that will just end up killing each other. So, the way that this pathway works, phytolankton produces dissolved organics, which get consumed most likely by bacterial plankton. And the corals love to eat bacterial plankton and zup plankton.

[00:09:03]That is how phytolanton plays out in most home aquariums.

[00:09:08]There are some niche cases where you pretty much have to have phytolankton.

[00:09:14]And one of them is my use case of laral cultures. Again, I've got a sea urchin program working. Sea urchin larve have a very specific requirement.

[00:09:25]But if you are doing zup plankton culturing, you want to grow some tiger pods or some rotifers, you're going to be culturing phto. I was talking to one of my colleagues in the industry and he was wondering why I'm trying to grow sea urchins when $10,000 angelf fish exists. He was like, with your skill set, why aren't you growing something that's a little bit more valuable at the retail level? And I told him that who knows that might be a future, but it all starts with your ability to culture phytolankton and work your way up the chain. Every aquaculture program starts at the base of the food web. So if you wanted to get into angelf fish breeding or clown fish breeding, anything of the sort, here is ground floor.

[00:10:17]As I mentioned before, most corals don't directly consume phyto, but there's a lot of things in your reef tank that do. Things like filterfeeding varieties of corals, for example, nonphotosynthetics, things like the dendronia, the scareneia, the chili corals. Certain leather corals are able to capture and eat phto. Beyond corals, you have filter feeders like certain buy valves, oysters, scallops. We even introduced a few flame scallops in our systems just to help knock down our level of phyto.

[00:10:58]And then you have things like tunicquetss and sponges. These are especially interesting because they are highly productive filter feeders to the point where they can almost act like aquarium filtration. Now, I'll point out sponges because remember when I was talking about ketocerus, it is a source of silicut. And the folks that are really serious about bolstering their sponge populations, they almost have to dose silicut in order to have those things grow. This is a much better delivery of silicut to those sponges cuz you're getting it in this perfect little capsule that also happens to be incredibly nutritionally dense. Another argument for sponges.

[00:11:40]Remember that dissolved organic issue?

[00:11:42]If you're experiencing high dissolved organics, sponges are really good at polishing that up. Obviously, you could resort to protein skimming and activated carbon, but this is a natural mechanism that you can also pursue.

[00:11:58]Last practical topic that I'll discuss here. There's a sliding scale of nutrition and convenience when it comes to things like phyto. You could get dried phytolanton foods. You can get frozen phytolankton foods. And then lastly, there's live. The dry being by far the most convenient, probably the most nutritionally incomplete because of all the different processes required to desiccate that.

[00:12:28]you're denaturing a lot of the healthy proteins and whatnot. If that's all you can do and you want to feed phto, it is what it is. Frozen, like with frozen micis or frozen krill, frozen phto is not too bad. Depending on how well it was frozen, if it wasn't properly frozen, the ice crystal formation ruptures all the cells. You basically have a nutritionally inert product. Once again, assuming that it was properly flash frozen, it is certainly a step up from the powdered stuff, but room for improvement. Lastly, you have the live stuff, which is what I'm using, and clearly the most difficult to handle.

[00:13:09]Very short shelf life compared to the others. You could probably squeeze about four weeks of shelf life in a refrigerator with most of these phytolankton, maybe only a week to two weeks with rodtoonus. Rotoonus is a special case. It is very delicate. I would treat live phytolankton like you would treat fresh produce. It's better that you use this stuff within like a week or two. But nutritionally, it is the king. If you're going to be going the route of live phto, feed it off quick. Or even better, try to culture it yourself. It's a fun project, and if you do it right, you get an everlasting fountain of nutrition.

[00:13:51]All right, guys, that does it from here.

[00:13:53]Hopefully, you learned a little bit about phytolankton, and perhaps we'll consider feeding it in your systems at home. Until next time, happy reefing.