Possible connection between captive seahorse diet and intolerance of high temps


Premium Member
I thought these statements by Dan Underwood, although they are based on anecdotal evidence, to be very interesting. They partially answered a question for me as to why so many people may have had better luck over the years with their horses at lower temps, when seahorses live in such highly variable temperatures in nature. Most species live in lagoons and grassflats where the temperatures can be hotter and more variable than the surrounding reef!! -which is incredible considering new insights on just how warm and variable in temperature the reef can be. The following posts are a very interesting discussion following Ron Shimek's article concerning just how warm and variable the reefs are. The stable temperature environment of coral reefs is a big myth- especially read the posts by greenbean36191:



Some species of horses are obviously from more temperate oceans. Even Hippocampus erectus however, a "temperate species" lives in colder water throughout most of it's range, but it ranges from Nova Scotia, all the way down through the Caribbean and down into South America!!!! If this really is the all the same species (which I don't think there is any reason to doubt), it would be interesting to know how much "hardwired" genetic differences with regard to temperature there are among different populations of this species. In other words, does it matter if your H. erectus came from Nova Scotia or Venezuela? Can a seahorse acclimate to a temperature range that is somewhere within the absolute thermal limits for its species? In nature H. erectus must be living in temperatures from the low 50's to the mid-to high 80's across its species range!! Also, from what we know of daily temperature fluctuations on the reefs (to say nothing of the even more extreme lagoons!!), temperature swings of >4-5 degrees in an hour are not uncommon. Many of us reefers would literally freak if this happened in our tanks but a huge body of research and experience is showing it really isn't a big deal, and is actually beneficial as it acclimates our creatures to a healthier temperature swing in preparation for when something might go wrong- and saves on energy costs!!

I am not advocating doing any of this in a seahorse tank. Just trying to reconcile what I see as a big discrepancy between the conditions necessary for healthy wild seahorses and healthy captive seahorses. I see Dan's comments above as a possible step in the right direction to understanding this. That the change in diet and perhaps other conditions in captivity make our horses much more prone to mortality at higher temperatures, temperatures that they would otherwise thrive in as they can and do in nature.

As a closing thought, consider that back in the day people believed that keeping SPS in captivity was practically impossible. Advances in husbandry including keeping very, very unnaturally stable temperatures (e.g. +/- 0.5 degrees) have allowed hobbyists to excel at this endeavor. Now that many other requirements of the SPS are being met (e.g. better lighting, filtration, etc.), the temperature stability and maintenance of lower temps (around 76 degrees) have been shown to be unnatural and completely unnecessary for success. I suspect this more conservative temperature regime was simply a band-aid for something else lacking which now is not needed...

Questions?, comments?, experiences? Please no fights- and this is not a justification to do something irresponsible with your tank occupants- but to understand in order to be more successful moving forward in the hobby.


New member
Although H. erectus is suppose to be the same species from both the northern and southern waters, there are some differences in them. Northern H. erectus typically have a larger dorsal fin, shorter snout, smaller in size and their fry are pelagic. The fry also reach sexual maturity faster than their southern counterparts. Also, those that keep the northern variety at cooler temperatures find them more active. Apparently they have done some adaptation.

I agree about the lagoons and grass flats. I have seen temperature fluctuations approaching 10 degrees with the change of tides and have seen seahorses in the flats at low tide when the water reached 92. In the local Indian River Lagoon, there are also large fluctuations in salinity, pH and O2 saturation.

I don't know what kind of sampling I get, but many of my customers are not participants on the message boards. Over the course of the last 10 years, it is quite apparent that those that keep their seahorses at lower temps have better longevity and less issues with their seahorses. There could be some other factors that come into play such as this group may be more conscientious with their husbandry, I don't know.

I have found that better flow, lower stocking densities, much better filtration, probiotics and adding Vitamin C to the diet helps with dealing with warmer temps and survival.

We still have a lot to learn!!!



Premium Member
Hi Dan! Great to hear from you! I have been lurking on MBI and soaking up a lot of the information you have provided there. I am really excited to try my hand at a little breeding, but will probably start with clownfish so that I have a chance to succeed at something before failing too much :)

I didn't realize that about H. erectus- somebody needs to some genetics! :)

Have you used UV sterilizers or noticed any benefit from them along these lines?


New member
Those that have bred both clowns and seahorses have reported the clowns are easier. Setups and methods are different though. We have seen many newbies to the hobby succeed with H. erectus. If you pick the right species, very doable.

There are ongoing studies with genetics. According to those who I have spoken to, testing does prove they are the same species.

UV sterilizers are good but not an end all. Most folks don't get the right power for the flow and system and don't pre-filter which limits their effectiveness. Also, UV are only effective on what passes through not necessarily what is in the tank. The real key is to remove the excess organics in the system. Seahorse tanks because of the way seahorses eat, their poor digestive system, the type and amount of foods they eat put a tremendous organic loading on a system. When this is addressed properly, the number of issues drops and success rates improve.



Active member

I have looked into this quite a bit, and while I am a hobbyist not a scientist there is quite a bit of information out there if you take the time to decipher it all.

For most the temperature regulation of 74F (not 75, not 73 but a max of 74F) goes back to studies done by Dr. Martin Belli. Dr Belli, or Labdoc on the forums is a board certified pathologist. Dr. Belli had the oppritunity to necropsy a very large number of hobbyists seahorses. He was able to identify bacteria that were the cause of infection, and in the case when he got them death.

I forget the excact equipment and methods that he used, I can find the book if you are really curious.

Basically he grew the samples out in his lab, and was able to identify several strains of bacteria, many of which were vibrio, but even several strains of vibrio. The strain was also not specific to the species which i found interesting. Erectus for example had IIRC 4 different strains cultured out of the same species. Reidi might share a strain or two, but then have others not in common.

In his lab he experimented with what happened to these strains of bacteria at different temperatures. Turns out that at 74F the strains changed. Once the strains hit 74F they became much more virulent. Stronger. The overall structure of the bacteria would change, I might not be saying this completely correct but you can buy his book, and a bacteria that was iiPP might now be IIpp. The reproduction rate could increase so dramatically with just that little temperature shift that the bacteria can now double every twenty minutes. 1 to 2, 2 to 4, 4 to 8, 8 to 16, 16 to 32, 32 to 64, 64 to 128, 128 to 256, 256 to 512... and that is in the first 3 hours. But with this bacteria you do not start with 1, you start with thousands. The exponential growth is insane.

Once you factor that exponential bacterial growth rate, coupled with a different structure a creature may have no built in resistance (the word resistance in accurate the word immunity is false I learned) to then you have a time bomb for serious infection to take place.

If you add in a stressor to that, an open wound, maybe the seahorse got stung by a coral, maybe it was wrestling with another seahorse and got cut on a rock...

The two together are a likely case of disease.

So how can seahorses live in the wild in higher temperatures and be fine?

The ocean is a big place. Our tanks are very small. Whatever size tank you have in your home, is very small in comparison. In the ocean there is a large dilution of this bacteria. Some even speculate there is a die off at deeper waters where the temp lowers and that bacteria becomes food... but that is not "FACT" yet.

When you have a hundred gallon tank and your bacteria is multiplying every 20 minutes in an ideal environment, (let's say 78F with nutrients in the water) the bacteria load difference between your hundred gallon tank and a 15 g tank is an hour. So having a "big tank" does nothing for you here. Having an ocean, well, dilution is the solution to pollution they used to say.

Now I have had this conversation with some people. They say (if you read the latter quote in a Bill Cosby voice it has much more effect), "Pledosophy, I do not want to buy a chiller, and I only have two seahorses, and my tank is 100g. It must be O.K for me to keep my tank at 80F and there be no problems. I will do a 20% water change everday if I need to".

Well, in a 100g tank, if you keep it at that high of a temp and say you were lucky that you only had one single cell of bacteria that was multiplying. You set this tank up on Sunday Morning. When you come home from work on Monday, your bacteria population count is now 1267650600228229401496703205376. That is the real number by the way for 33 hours and 20 minutes of growth (2^100).

People often suggest doing weekly 20% water changes. Got news for you, at those temps hourly 20% water changes are not going to do a damm thing for you in way of bacterial control.

There is good news here though. Until they reach the temp of 74F those bacteria maintain a more passive stance, one a seahorse can have some resistance too, and they hardly reproduce at all. The lower temp creates a far less virulent bacteria that does not reproduce as quickly.

Now if you have followed seahorse husbandry in relation to disease you will often see this as the first two steps to treat an ill horse. Isolate the seahorse (so the bacteria does not spread to others), lower temp to 68F.

Why 68F? Well as it turns out those strains of vibrio that affect seahorses go almost dormant at 68F. So whatever bacterial infection is present, stops.

Back before we knew why, many breeders were keeping fry at 65F. There survival rates greatly increased and it was widely speculated that the lower temperature had an affect of the metabolism of the seahorse. I didn't even know how to pronounce vibrio, but I know I had better luck rearing fry in the winter. Maybe more then just metabolism was in play. . .

In the topic thread you mention diet, and I do believe that can be a factor as well in our systems, especially those with higher temperatures and lower turnovers.

Seahorse keepers want to feed frozen food. It is sooooo much cheaper it is ridiculous. My tank now, would cost me $30 a week to feed live, but frozen is like $4 a week. The difference is amazing.

Another difference is though, with a tank that does not have the appropriate flow, meaning it is designed not to allow extra food to accumulate untouched in the rock work to breed disease and such and possibly later be injested by a seahorse after it is dislodged from the rock, frozen foods can be dangerous. You have to plan for them IME.

I do not think that is a food or diet problem as much as it is a tank setup issue. It is possible to setup a tank so that the frozen food will not accumulate and decay in one region.

While this is true live food does have an advantage that it is not rotting and contributing to waste until it is consumer. But, feeding live long term can cost thousands of more a year per seahorse, and is often unreliable at the source IME.

JMO on the matter, always love the discourse on this ideology.