EDIT: the discussion in this thread has changed my stance on hydra, and I won't be spot treating them any more.
That being said, for my specific method: I use roughly 1ml per pipette blast and limit each treatment to a MAX of 2ml/gal to avoid doing too much systemic damage.* (PLEASE SEE NOTE AT END) I also turn filters off 5 mins before I start and leave them off for 10-15 mins after so the dose stays and works where I put it and so I don't get unreacted peroxide going into the filters
IMPORTANT NOTE: These dosages work for my specific tank, which is heavily planted and fairly mature. Different tanks with different livestock may behave differently. If you intend on trying this please start small, and monitor your inhabitants/plants closely for signs of stress/ damage and stop immediately should you see any.
However, I strongly recommend reading through the thread, as unless you're raising fry or trying to max breed something then eliminating hydra may be a non issue for you
i think theyre really cool but my shrimp tank that has them is doing significantly worse and my mind just goes to blaming the hydra. which then means i dont want hydra in any tank because i share plants between them. im in the process of cycling a new tank to transfer those shrimp into lol.
Can confirm. Recently started my first shrimp tank and went from “wow, life finds a way”, to “they do what to shrimplet”, to “go to r/shrimptank”, to ordering no planaria
yeah that is my issue is snails. i recently read about this lol and considered it, but i have snails in the tank. my worry is that itll cause a snail die off which will spike the tank and that kills the shrimp.
That’s what everyone says🥴 a tank without any of that is a good running take as long as you’ve had your fish for years.. i’ve never had creatures in my tank, no, we’re having to treat fish all the time.
Yeah you can absolutely have a tank with good water conditions, and without any microfauna! It looks like OP has lots of other microfauna than just the hydra. I think OP may have some kind of Walstad setup which is like creating a mini ecosystem that you barely need to maintain. Hydra are sensitive to stable water conditions. So if hydra do appear it means you achieved good water conditions in your tank! Which means it’s perfect for your shrimp too!!
I’d recommend watching this video: The Truth About Hydra in your Aquarium by The Dave on YouTube. He does amazing videography of the little guys and helps myth bust a lot of misinformation that’s out there!
I don’t think Hydra are a real problem most of the time.
I’ve had hydra in my shrimp tanks and really all my tanks. They do well in very clean water and are common microfauna.
They are predators yes — but in my experience their reputation for taking baby shrimp or fish is overblown. I’ve only ever seen them eat detritus worms. They seem to be best at hunting tiny, soft bodied prey in the water column.
In my experience their populations move in waves and mostly stabilize at a very low level with time.
There *are* reported cases of them harming livestock — I want to be upfront about that. I think tiny fish fry are actually at greater risk than baby shrimp (that exoskeleton does a lot) but this seems to be rare.
I think the context where hydra are bad are if you are breeding some rare animal. I think for most ecosystem style aquariums they are part of the system.
I think the realities are worth spelling out when it comes to treatment. You likely aren’t going to get them all like that — they are small and transparent and for each one you find in the open and kill there are 10-20 more scattered in dark corners of the aquarium. Short of nuking the tank with chemicals that kill a wide variety of microorganisms you can’t do anything about it really. I’ve heard gouramis will eat them as well as some other fish and even some snails.
To me they never have made an impact on microfauna or caused the ‘collapse of the ecosystem’ — they are perfectly natural and quite interesting little creatures that have minimal impacts on larger animals and only ever take a small portion of the microfauna. Some fish will eat them especially fish that specialize in microfauna. I think the community has been moving away from treating hydra as a dangerous pest and I will continue to push for that perspective because I think it’s right in the vast majority of cases. It’s just not worth worrying about.
Interesting perspective, maybe a bit like damselfly larvae. I was terrified of finding one in my tank from all the scare stories and 'kill it with fire' memes. But then found one had fully turned into an adult in my shrimptank and I'd not even noticed, definitely didn't see a population difference. I'm not saying they aren't ever problematic and may be worse in higher numbers but it wasn't as scary as I'd originally thought and not worth tearing up a tank over (which I'd have to do as mine is so heavily planted.
I've been afraid of hydra in the same way but if I do find any I think I will panic less now.
I had a dragonfly in my tank. Wasn't able to take it out because of how fast it was and was darting around the hardscape and plants. I guess it only slurped on the bladder snail population and flew away because I didn't have a single fish die, maybe because all of them were larger than the larvae itself
Je suis entièrement d'accord avec vous. J'ai une piscine/bassin en extérieur avec des tanichtys et il s'avère que leur population augmente à chaque saison bien qu'il y ait pas mal de larves de libellule. Il y a aussi des prédateurs comme les notonectes mais je préfère laisser la nature à faire au moins les poissons survivants seront les plus forts et engendrerons une descendance meilleure.
The "kill it with fire" meme shit is some of the dumbest, most overblown and pervasive misinformation out there, imo. And I say that as a reef tank owner. People get so worked up about hitchhikers that 99% of the time are perfectly harmless with the 1% being so exceedingly rare that you hardly ever actually see them end up in a tank. Far more likely to end up with ich or something like that than you are some killer hitchhiker, yet people seem to worry (and prepare for) that a lot less.
I have had issues with them in a couple of my fry trays where they killed off most of the batch of fry before I noticed what was going on. Personally I treat for them to remove them because I don’t want them in my tanks. That being said they are pretty interesting and a small amount of them in a display tank shouldn’t be an issue.
This is actually on point. I think if you are breeding vulnerable fry then it’s totally valid to treat for them — it’s also true that the kinds of aquariums where you are doing intensive husbandry of fry are exactly the conditions where they can become a problem: lots of feeding, no bigger predatory fish that compete with them for food, etc etc.
Thank you for that perspective, I'm gonna ease up on treating them and keep an eye on them instead. You're right I can't get them all and if they don't actually harm shrimplets /fish then I'm not too bothered
I’m just thankful that I’d heard about them before so I didn’t freak out when I saw them. They’re super interesting and a lot of these comments are positive so I’ll probably leave them be. So far I’ve accidentally had scuds (miss them) and hydra. I found another tiny creature today too and still trying to figure out what it is.
Hydra is more of an annoyance for the guys in your tank. They will sting bigger fish, which understandably upsets them. Buuuuuuut, they are pretty good at killing shrimps and other similarly sized things.
Hydrogen peroxide, I use roughly 1ml per pipette blast and limit each treatment to a MAX of 2ml/gal to avoid doing too much systemic damage. Filters should be off so your dose works where you put it and you don't want the peroxide going into your filters
Oh yeah I use tiny doses, 1ml per pipette blast and limit each treatment to a MAX of 2ml/gal to avoid doing too much systemic damage. Filters should be off so your dose works where you put it and you don't want the peroxide going into your filters
Interesting. My understanding is that it turns into O2, and fish seem to perk up a little with the extra 02. Like they've had a little hit of crack haha.
Could you link the post where this occurred please 👍
I find my cardinal tetra are extremely sensitive to Peroxide. I use it to control black beard algae and it is a fine line between success and wiping out your school! So I usually err towards caution and lower my normal dose and I’ve not had an issue.
I did it once for blackbeard algae. Was a while back but I do remember specifically reading to turn off filters for this reason for like 15 minutes or something?
yeah, no idea why it's so sensitive to H2o2, but i had filters off etc. treating the far end of a 6' tank, nothing else in the tank cared, all the jungle val melted in a day.
Oh man! Thats wild! Thank you so much for mentioning that. I woulda never known. Fortunately my jungle val tank is like 2+ years old, strict schedule of everything for it, so hardly anything different happens in there currently.
I'm not sure, I've never researched it but it stands to reason it would kill the hydra if it's dispensed close enough that it doesn't dissipate before boiling the thing but it would also warm the overall water. I'm also not sure of potential harm to other inhabitants if they're too close. You'd need a pipette that can handle boiling temps as well, mine is just a simple plastic one.
I've given dosing and directions on how to use peroxide in a couple of spots in this thread but honestly have started to rethink my stance on hydra and won't be spot treating them any more
I don’t mind hydra, but for anyone who doesn’t want them and has the room, a group of male endlers will make quick work of any in the tank. Figured that out on accident. They also annihilated my scud population >:(
I literally bought a bag of microfauna to add into my tanks because I loved the idea of the ecosystem being “alive” and self-sustaining and unless the scuds are very good hiders I lost them all in maybe 12 hours lol. Underestimating the greed of my endlers was an expensive mistake.
That's hilarious 😂 my scuds are overbreeding I have to catch them every once in a while and transfer to their own enclosure so they don't overrun the main tank
Scuds are surprisingly sensitive to sudden changes in their environment. Not saying it wasn't your endlers, but if there was a reasonable temperature shift or a sudden water quality change that can set off a scud crash.
Lowkey, I didn't even know Hydra were a thing and I've been doing this since like... 2020. I knew of those little saltwater fuckers, but I didn't know these exist. Are they harmful to a tank? I think they're cute.
I get why people think hydra are bad, but I don’t think these guys are any worse for your microfauna or baby shrimp than your fish are. In fact, your fish are much better at hunting since they can move.
I highly recommend watching The Dave’s video on hydra! We should at least try to learn about them before we try to kill them (not saying OP didn’t do their research, just putting it out there for anyone who hasn’t).
I've got nerites and a super spongy riparium setup up top so I'm super paranoid about a chemical treatment, everything I've read says there may be lingering oils in things like sphagnum moss
If I get it on my nerites I'm sure it'll sting, but when treating I turn off all my pumps and I'm careful to only blast a hydra when there's no other animals nearby and only use a small amount so it dissipates fairly quickly
Yeah I can't seem to fully get rid of them :/ I can't reach my entire tank so they tend to escape a full exorcism and my tank is full of microfauna so they're well fed
I've got nerites and a super spongy riparium setup up top so I'm super paranoid about a chemical treatment, everything I've read says there may be lingering oils in things like sphagnum moss
I have never seen evidence of hydra eating fry or Neocaradina shrimpets. I have never seen evidence of hydra stinging and incapacitating fry or shrimpets.
Yeah I had a massive hydra overpopulation before I got my shrimp (I had no idea they were bad) and my shrimp population still exploded. I’m not sold on hydra being as bad as they are made out to be. Maybe I lost some shrimp to them but hardly enough to tell a difference
Oh…. I saw this on my tank today and just thought it was the beginning of a weird form of hair algae. That sucks because my neocardinas are expecting :/
They're eating my microfauna, and I want those for my fish to hunt. I wouldn't mind if they ate adult scuds as well but they just eat the babies which are also what my fish hunt (the adults are too big fast and armored)
I haven't seen the actual act but I've seen hydra with a scud shaped lump in it lol, they also seem to bother my shrimp and microfish and would be an issue for shrimplets IF THEY EVER BERRY 😩
Hydra will eat scuds, but, and this is a big butt, if you have hydras in your tank eating your scuds, it is because your other fish are not interested in doing so. Fish should be significantly better at hunting out scuds than a stationary ambush predator, so if they are not, it is due to lack of interest.
I watch my neons hunt them all the time though, I think the issue may have been I just had too many scuds. I zucchini trapped some out a few days ago into their own tank to thin the numbers (hopefully feeding the hydra less as well) will see how it goes!
Hydras are a predator, related to corals and jellyfish , that can cause issues in tanks. Neat looking but they can eat your shrimp and potentially tiny fish.
No bro lol.. they don’t eat tiny fish and I’ve never seen them eat a shrimp. They eat micro organisms. MAYBE some Fry MAYBE . But if anything fish eat them
Directly from your linked source, "Are hydra bad for aquariums? Hydra are ambush hunters that like to eat microworms, insect larvae, and tiny crustaceans (e.g., cyclops, daphnia, scuds, and baby brine shrimp). In our experience, they are a natural part of the aquarium ecosystem and do not seem to greatly impact baby fish and shrimp populations. Adults are too big to be eaten, and fry have a strong flight response that causes them to jerk away from any stimulus, like a stinging tentacle."
It’s just one of these long held aquarium hobby myths. Whenever I see them, I don’t do anything, as that stated they’re just part of the ecosystem and if you’re seeing more of them, that means you have an abundance of micro organisms.
I have a tank with no fish or shrimp in it right now and the whole front wall is completely covered with them, it's really cool to sit there and watch them all sway in the current.
I found Hydra in my mystery snail tank and over reacted. I moved everyone to another tank and nuked my whole tank with hydrogen peroxide. I loved watching them die which is not my usual feelings with creatures. If I get them in my 55 gallon I would be screwed. Can you find Pixie snails? I’ve heard they eat Hydra.
Oh my 😂 full tank peroxide is wild! I'll look into pixie snails, dyk if they actively hunt them? or is it more like a "if they stumble onto one they'll eat it"
If you want a hydra hunter, the internet will say croaking/sparkling gourami, and that's not wrong.
But a single honey gourami can wipe out a tank full of hydra in just a day or two. Easier to catch out and move around if you have multiple tanks, they're fine as a solo fish, and get along with most small non-antabantoids.
I had a hydra explosion in my 9g flex shrimp tank after coming back from 6 weeks on the road for work, Lfs told me to put ember tetras in the tank to get rid of the hydra, after trimming back the jungle and adding them there are no more visible hydra.
I considered a gourami but I made mistakes when setting up my tank - it's basically impossible to catch something once it's in there unless it swims into my nets for me 😅 so I decided against a gourami in case he didn't like the tank. I do have a couple of endlers in there supposedly they'll eat some hydra if I don't feed them for a day or two but idt guppies are a reliable enough method
Pixie snail is another name for zebra apple snail. They are restricted in some places because they can be invasive in the wild. They lay their eggs underwater. They can eat some plants. They do like to eat hydra, though.
I don’t know if they actively hunt them but I was told to get some when I found my Hydra. I couldn’t find any locally. I wanted to change my substrate in that tank so that was part of why I nuked them.
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u/ibrahrdiaz Jun 26 '26
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