What did I do wrong?


New member
I've been in the Hobie now for about seventeen years. So I know a lot about reef tanks. I have a 200g mixed reef with all the bells and whistles. I set up a 24g JBJ nano tank just for sea horses. This is my second attempt in trying to care for them. I have had three horses for about six months with no problems. The tank has been having trouble with red cyno. The first time I had a horse tank I had the same red cyno problem so I used the cyno remover and killed my horses. I figured it was the cyno remover chemical that killed them. So last night I decided to try and deal with the cyno attack. All I did was siphon the cyno off the sand and the rocks. I also did a 5g water change using RODI water. This morning to my surprise, one of my horses was dead. Another is in critical condition and my third one is breathing fast. I've added a phosband reactor off my big tank full of carbon.

What did I do wrong? I am very up set.


the H is silent
As a novice who has only set up a seahorse tank and no reef experience, a couple of things that I can see might have relation:

1. Depending on breed, 24g is potentially too small for 3 seahorses.
2. Depending on the depth of the sand bed, you might have stirred up some stored evil stuff when siphoning and it shot levels way up?
3. What temps do you run on that tank? Higher than 74f the bacteria can populate too fast and overwhelm the horses.


New member
I cleaned mine out like you are talking about about three months after I got them ,about a year ago, same thing mine went into shock, and my water per. were the same as the new water I added, I took my horses and placed them in another tank for a few days and then put them back in there tank, ever thing went fine then.( mine didn't die,one was upside down in the water for a few hours(I think he was just a drama queen tho)
I just let mine grow up now for several reasons, and the ponys like it better.My tank just don't look as good, but my water per. has been perfect for almost a year now without any water changes except for a few gallons taking out here and there for baby's.
Sorry for your loss tho. Let us know how it goes.
Maybe RAYJAY or PEKA will give a reason for this and some better advice !


New member
JBJ nano cubes are known for getting hot, in the upper 70's to low 80's. I agree with Molehs on this one. Ive always kept my seahorses at around 72, sometimes it even goes down to 69 at night and ive never had a problem. Anything over 74-75 is asking for trouble with seahorses in my opinion.


New member
You may never know the actual cause without doing a pathology examination on the dead. Best guess would be from having too many seahorses for the size of tank.
As already mentioned, temperature range may exacerbate the problem as bacterial growth is exponential as water quality degrades and temperatures rise above 75°F.
Maybe if you check the links at the bottom of "My Thoughts on Seahorse Keeping" you could gain some insight into possibilities.


New member
OK all you sea horse people should just kick me between the legs. Like I mentioned I have been in the Hobie for seventeen years. I guess I thought if I could keep a large reef tank for so many years, I knew everything. Well I definitely screwed up. I did not resource the care of sea horses. I thought the horse tank was the same as keeping a reef, but with no fish, because they will consume the food faster then the horses could get to it and slower flow. I know now I am completely wrong. After doing some resource I know I've lost two of my three horses do to heat and bacteria.

Do to the cyno problem I siphoned the cyno and did a 5 gallon water change. I had a heater in the filter system and did not unplug it when I did the water change. Guess what? The heater staid on. Tank was at 80 degrees.

Now I am doing what I should have done in the first place, resource. Can you guys please help me in learning about the care of keeping horses? My nine year old daughter is ****ed at me.

Here's my tank set up.

24 gallon JBJ tank.

I only use one sponge in the first camber of the built in filter.

Second chamber I had a heater (gone now) and a bag of carbon.

Besides the main pump the tank came with, I run a small maxi jet pump in the tank.

The factory JBJ hood has been removed. I have a DIYS Cree LED lighting (dim-able) hanging twelve inches above the water.

Horses were feed every night with mysis.

5 gallon water change every month.

I've removed the two soft corals from the tank, do to the colder water I must have. Will be looking at putting in some nice looking algae.


the H is silent
Can't speak directly to mechanical filtration but check your numbers regularly as horses create a lot of ammonia and you need to be sure you have enough good bacteria to support that. As well make sure any intakes are guarded to prevent a horse from getting sucked up or unable to swim away. Sounds like the lights should be fine, just enough to illuminate.

Generally temps between 68-74 are good. Most seahorse owners will tell you to feed at least twice a day.

I come from the other side of the fence of not having a tank of any sort for at least 20+ years and spending the last year researching and building up to finally get my first horses a few weeks ago. From my observations you will find that most seahorse people feel that they are much more than just "fish" and are very willing to give advice and help to make sure that someone has success with seahorses.


New member
Well, I've never used a plug'n play tank so I can't help much with that.
Forget water changes of 5g once a month as 5g once a week should be a minimum with larger changes recommended.
For seahorses you have to have exceptionally clean water, better than a reef tank. As you are already working with a tank a bit smaller than recommended for a pair of seahorses like reidi or erectus, you need to be more diligent with your husbandry. Even a skimmer added can help.
Also be sure to remove any uneaten food at least daily and preferably about an hour after feeding. Use a turkey baster to blow detritus and uneaten food from around rockwork and hitches so it can be removed. Leaving these deposits just provides bacterial farms a place to grow.
By the way, if you've read the "MY THOUGHTS" write up, then you know I too thought I knew enough to keep seahorses any way I wanted. I'm starting into my 19th year of reefing in January.


New member
Bacteria can grow fast but still, death overnight is far more likely to be attributed to low oxygen if the water parameters were normal. Between the high temperatures, the closed top, the bioload, and whatever disturbance the cyano siphoning caused. Any parameters thrown off would exacerbate the problem.

Like has been said above, the lower temperatures help keep bacteria at bay, which can be a real problem with seahorses. Stability of temperature is also important. Lower temperature also gives you room for error and allow more dissolved oxygen. For most species available, I'd try to stick it around 72*. With how small the tank is, I'd use a chiller, unless you keep your house at 70* year-round. Trying to rely on evaporative cooling in only 24 gallons would worry me.

A lot of soft corals and macro algae can handle the cooler water fine. It is the low-output lighting most people use to help with heat that becomes the problem, but if you have enough light, you should be fine.

Keep a close eye on your parameters, if ammonia, nitrite, and nitrate are all staying at zero with only monthly water changes - first buy a new test kit, but if that says the same thing, then congrats :) Otherwise, adjust your water change schedule to match. I would also purchase a skimmer for such a small body of water.

The amount of space actually available in a 24 JBJ isn't going to do seahorses justice, but if it is what you are absolutely going to use, I really wouldn't go with more than two seahorses and no other fish. And do everything in your power to maximize space in the water column.

To remedy what has gone wrong so far, to help the remaining seahorse, I would do a large, 50% ish water change (or a 100%) to dilute bacterial colonies (be particular about matching all parameters), and reduce the temperature by 2-4 degrees per day, initially reducing it all the way to 68* for a few weeks.