How do I properly care for a freshwater blenny

So I’ve just purchased my first blenny a top hat blenny and I’m not sure what their requirements are I’ve dealt with similar fish like emperor gudgeons, peacock gudgeons, and bumble bee gobies but this is my first blenny I just had to pick him up since I adore unusual fish and for a top hat blenny he was fairly cheap only being $35.00 I have two tanks he could go into a twenty that I’m going to restart and a established sixty gallon tank that has community fish I’ve looked all over for proper info on these fish but I’ve come up with nothing so if anyone could help I would be very grateful here’s a picture of him

 

I didn’t find a ton of info, but I did find some. This species mostly tends to be brackish, but can live in salt or fresh water. This article has a maintenance section lower down on fresh and brackish water blennies. They need low nitrate and like cooler water with a lot of oxygen. They also aren’t community fish as they will eat smaller fish. Check out the article and do your best. Good luck!

 

Hey thanks for the info luckily I had an empty twenty gallon tank to spare wich hopefully gives him enough space I had no idea that they could be so territorial can you suggest any suitable tank mates

 

I really don’t know much about tank mates. I know they can be fin nippers, can eat small fish, and can be vulnerable to aggressive fish. That narrows down the options a lot.

 

Well with that info I’d say the best option is a large peaceful top dwelling fish which their are a couple such as hatchet fish, rainbow fish, gouromis, angel fish, and possibly discus but I don’t have the tank for a discus so probably one of the other options could work maybe even keyhole cichlids would work but what to put in between the two is the real question perhaps a larger tetra species like bleeding hearts, black skirts, or Colombian tetras so while yes maybe not a huge amount of options I see some potential tank mates that suits these requirements enough to make an established tank because as much as I love the top hat blenny I’m not going to dedicate an entire twenty gallon tank to a three inch fish that is often hiding that just seems Unnecessary

 

Well with that info I’d say the best option is a large peaceful top dwelling fish which their are a couple such as hatchet fish, rainbow fish, gouromis, angel fish, and possibly discus but I don’t have the tank for a discus so probably one of the other options could work maybe even keyhole cichlids would work but what to put in between the two is the real question perhaps a larger tetra species like bleeding hearts, black skirts, or Colombian tetras so while yes maybe not a huge amount of options I see some potential tank mates that suits these requirements enough to make an established tank because as much as I love the top hat blenny I’m not going to dedicate an entire twenty gallon tank to a three inch fish that is often hiding that just seems Unnecessary

From what I've read on them (you're right, there's not a lot out there), they're not likely to survive long term in freshwater. Presumably they're one of those species that can tolerate zero salinity temporarily, but will suffer poor health and eventually succumb to it if unable to return to brackish over time.

Given that, perhaps stock the 20g with fish that have similar requirements, or at least a strong tolerance for salt?

Honestly, for a fish that cool I'd gladly keep it solo in a 20 gallon brackish setup. But maybe that's just me. I'm more interested in recreating ecosystems and keeping interesting fish than I am in lots of flashy movement. In fact, of the three tanks I'm looking at in my living room right now, I can't see a single inhabitant

 

what about a few mollies? You can't add very many to a 20 gallon, but a few should be fine. They're big enough to handle aggression from the blenny and can also switch to brackish if needed. They also won't be able to overpopulate because the blenny can eat the babies.

 

Wait there are freshwater blennies?!!?? I thought blennies are so cool and I thought there weren’t any. I’m following this thread

 

what about a few mollies? You can't add very many to a 20 gallon, but a few should be fine. They're big enough to handle aggression from the blenny and can also switch to brackish if needed. They also won't be able to overpopulate because the blenny can eat the babies.

That's exactly what I was thinking! A few wild type sailfins could be really handsome in there.

I did just do a little more digging based on the latin name, and came up with some more info to support the theory that keeping it in pure freshwater isn't sustainable.

The ICUN Red List's page on the species describes them as marine neritic, and of the habitat says:

Habitat and Ecology
This species is reported to occur in brackish water and oyster beds (Springer and Gomon 1975), and in shallow rocky areas of estuaries and bays. They attain less than 6.5 cm SL.

Another site, fishbase, says that "Adults rarely enter brackish water." I imagine that means that they rarely enter brackish from seawater, not from fresh. This is my assumption based on the fact that distribution maps highlight the sea coast around japan as the habitat. The statement is cited - Breder, C.M. and D.E. Rosen, 1966. Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p.

I can't find a digital copy of the publication online (yet) to get more info in context, but there are copies available at libraries near me. If I can't find it online I might go take a look at the book this week.
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Update:
Did a little more digging cause this one has me super curious. I love it when the internet doesn't just give up the answer. The WoRMS database lists this fish as strictly marine, not brackish or freshwater. I also submitted a request for a page scan from the American Museum of Natural History so we can see what that book has to say in full (gotta take advantage of the gf's student status as much as possible, right?). Hopefully they'll get in touch soon!

 

That's exactly what I was thinking! A few wild type sailfins could be really handsome in there.

I did just do a little more digging based on the latin name, and came up with some more info to support the theory that keeping it in pure freshwater isn't sustainable.

The ICUN Red List's page on the species describes them as marine neritic, and of the habitat says:

Habitat and Ecology
This species is reported to occur in brackish water and oyster beds (Springer and Gomon 1975), and in shallow rocky areas of estuaries and bays. They attain less than 6.5 cm SL.

Another site, fishbase, says that "Adults rarely enter brackish water." I imagine that means that they rarely enter brackish from seawater, not from fresh. This is my assumption based on the fact that distribution maps highlight the sea coast around japan as the habitat. The statement is cited - Breder, C.M. and D.E. Rosen, 1966. Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p.

I can't find a digital copy of the publication online (yet) to get more info in context, but there are copies available at libraries near me. If I can't find it online I might go take a look at the book this week.
______________________________________________
Update:
Did a little more digging cause this one has me super curious. I love it when the internet doesn't just give up the answer. The WoRMS database lists this fish as strictly marine, not brackish or freshwater. I also submitted a request for a page scan from the American Museum of Natural History so we can see what that book has to say in full (gotta take advantage of the gf's student status as much as possible, right?). Hopefully they'll get in touch soon!

I saw lots about that brackish vs fresh vs marine issue. I was thinking of bringing it up, but I wasn't sure. I think it may be similar to a bull shark. Can live in freshwater for a period of time, but won't necessarily thrive. I think a brackish tank will definitely be beneficial long term. And I for sure agree with the wild type sailfins! Those would look great!

 

I saw lots about that brackish vs fresh vs marine issue. I was thinking of bringing it up, but I wasn't sure. I think it may be similar to a bull shark. Can live in freshwater for a period of time, but won't necessarily thrive. I think a brackish tank will definitely be beneficial long term. And I for sure agree with the wild type sailfins! Those would look great!

Yeah, I was hesitant to mention it until I'd found info on more than just the one reddit thread. nobody wants to be a google search know it all, lol. I'm wondering based on that morsel of info on fishbase if they're an anadromous species.

 

Yeah, I was hesitant to mention it until I'd found info on more than just the one reddit thread. nobody wants to be a google search know it all, lol. I'm wondering based on that morsel of info on fishbase if they're an anadromous species.

Yeah, I saw that thread too. I was afraid to say that in fear of appearing overly confident and then proven wrong by someone who knew more than me. It's totally possible and would make a lot of sense for it to be anadromous. That would explain how controversial the topic of fresh vs salt seems.

 

Yeah I can pick up some brackish mollies my only problem is I don’t know how to properly set up a brackish environment
do you think I could keep it with a glass fish they can tolerate brackish water right

 

Yeah I can pick up some brackish mollies my only problem is I don’t know how to properly set up a brackish environment
do you think I could keep it with a glass fish they can tolerate brackish water right

What species are you looking at specifically? I don't have any practical knowledge, but I think they're brackish the same way your blenny is freshwater. Does the Glassfish, Parambassis ranga, need salt?

 

That's interesting, I thought they were full brackish. I know they can't be a completely freshwater species as I've seen them live very happily in a friend's brackish tank, but it's cool to know they can live in fresh.

What species are you looking at specifically? I don't have any practical knowledge, but I think they're brackish the same way your goby is freshwater. Does the Glassfish, Parambassis ranga, need salt?

 

That's interesting, I thought they were full brackish. I know they can't be a completely freshwater species as I've seen them live very happily in a friend's brackish tank, but it's cool to know they can live in fresh.

very cool! from my limited knowledge there are a few different but similar species of glassfish, and tolerance for salinity varies among them. Do you know if your friend's are p. ramba? That would be an awesome tank mate, and more geographically appropriate than mollies (though I still love a wild sailfin....)

 

So the only glass fish I know that can tolerate a completely freshwater tank is a colored glass fish a genetically engineered glass fish that has been made similar to that of the common glo fish tetra you see today but this glass fish came far before the modern glo fish

 

So the only glass fish I know that can tolerate a completely freshwater tank is a colored glass fish a genetically engineered glass fish that has been made similar to that of the common glo fish tetra you see today but this glass fish came far before the modern glo fish

Oh, yeah I know those from when I was a kid. Pretty sure they're injected, not genetically engineered. GloFish pioneered that process and patented it to the moon and back. Unless you're outside of the US?

 

so I’ve run into a slight problem I’ll probably need a bottom feeder to help out with cleaning up the tank but these blennies are particularly territorial twoards other bottom feeders including their own kind at lest others males I’m not sure how they respond twoards females but that doesn’t particularly matter since it’s not really the greatest bottom feeder and I can’t get my hands on another one of these blennies for the cheap price that I got it for let alone find a female I took into account that knight gibies where their but they are somewhat also territorial twoards other bottom feeders so the only reasonable option I could fin is the larger variants of the banjo catfish that can actually tolerate brackish conditions so anyone have any input to help out I mean the mollies could cover it but I want one other fish that’s going to be actively staying in the bottom so any thoughts this is a really big step in my aquarium hobby this brings me one step closer to being able to maintain a marine tank

 

so I’ve run into a slight problem I’ll probably need a bottom feeder to help out with cleaning up the tank but these blennies are particularly territorial twoards other bottom feeders including their own kind at lest others males I’m not sure how they respond twoards females but that doesn’t particularly matter since it’s not really the greatest bottom feeder and I can’t get my hands on another one of these blennies for the cheap price that I got it for let alone find a female I took into account that knight gibies where their but they are somewhat also territorial twoards other bottom feeders so the only reasonable option I could fin is the larger variants of the banjo catfish that can actually tolerate brackish conditions so anyone have any input to help out I mean the mollies could cover it but I want one other fish that’s going to be actively staying in the bottom so any thoughts this is a really big step in my aquarium hobby this brings me one step closer to being able to maintain a marine tank

my friend! may I introduce you to punctuation? lol

you don't need a bottom feeder to clean for you. just maintain the tank. if you're cleaning your substrate weekly during water changes, you're fine. bottom feeders aren't our janitors, no matter how much we wish it were so!

You have the fish you've got now, and the best thing you can do is built a suitable tank and community around it, unless you're interested in rehomeing or returning it to the store. Honestly I think the first step is determining the salinity you'll be keeping it at. That will narrow down your options for tankmates. Your options are already limited, but don't try shoehorning another species into your tank just because you want it to be fuller. It won't end well.

Imo, you really don't want to be looking for fish that "can tolerate" salinity. Though tolerance alone seems to be the gold standard as far as retailers justifying the sale of fish as brackish or (in the case of this goby and some puffers, etc. freshwater), you don't want your stock to only be able to tolerate the conditions you put it in. I can tolerate 30 degree weather in nothing but my underpants, but I sure as heck can't live that way long term. Once you've got the SG you're keeping the tank at for the goby settled on, then it's time to consider additional stock. It'll want lots of nooks and crannies to explore in, too, so you want to scape the tank appropriately before picking tankmates as well. I bet if you create a really great environment for it, this goby won't be as shy as you imagine it will.

 

These guys are known for being super active. I don’t think you’ll have to put anything else in there to get plenty of activity towards the bottom. The catfish gets too big for this tank as well. The mollies can handle cleaning algae and food leftovers. If you really want another fish species, you can maybe do a few golden wonder killifish or something similar, but nothing else. You don’t want to risk overstocking.

very cool! from my limited knowledge there are a few different but similar species of glassfish, and tolerance for salinity varies among them. Do you know if your friend's are p. ramba? That would be an awesome tank mate, and more geographically appropriate than mollies (though I still love a wild sailfin....)

I believe they’re ramba. The tank isn’t super salty, but it’s definitely salty enough to be considered brackish . I agree, it would be much more appropriate geographically.

 

Did either of you manage to view the reef2reef article on these guys? it was the top result on google but when i try to view it i keep getting a server connection error. I just tried running the URL through the wayback machine and they have it archived! so if you were running into the same error, here's the page. it's VERY informative - if reliable, clears up a lot of the issues we're talking about.
Successful Captive Breeding of the "Freshwater" Tophat Blenny
At first blush, it looks like 5ppt salinity/1.0038 SG is a safe place to start.

 

There is only one species of truly Freshwater Blenny, Salaria fluviatilis. Found in lakes and streams around the Mediterranean basin, gets close to 6 inches. The others are brackish-tolerant or Marine in nature. Some unscrupulous fish shippers have been selling some of the brackish-tolerant species as "FW", but they are not capable of surviving true FW.

I have wanted to get some true FW Blennies for a long time, but they are apparently becoming endangered.