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Nano Rockpool Biotope??


Crabby
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I have an idea.

And considering I’m terrible at being concise, I’m sure it’s gonna take me a while to explain it.

Essentially, I want to do a nano marine rockpool tank, with just crustaceans and molluscs (and perhaps a seastar or two). And I really don’t know how plausible it is, but I’m pretty intent on finding out. I don’t know if anyone here has any experience with marine shrimp, but I figured I may as well see if any of the Aussies here are familiar with the shrimp I want to keep. Or if there’s a nano marine expert who can help me out. Or if anyone just has any advice. I’m all ears.

So this species of shrimp is actually the species that got me into the hobby! I found them on a camping trip, and they were just so active and engaging, and I just fell in love. Then I went home, did a bunch of research, and got an aquarium. They’re part of the reason why I’m so interested in shrimp. Now I’m on holidays again (in a different place in Victoria, Australia) and they’re everywhere in the tide pools. Millions.

The species is ‘palaemon serenus’, the red-handed shrimp, and they grow to about 6cm for big females (which I discovered last night) and I think 3-4 for males. Just from observation. They live primarily in colonies of 10-30 under rocks during the day, venturing out when they feel safe, and going everywhere once it gets dark. They’re omnivorous, eating pretty much everything they can get their little claws on (including my fingers and toes). They look rather like Australian freshwater macrobrachium shrimp, to be honest.

I’ve had a look and it’s legal to collect from this location. There aren’t limits on anything I want to collect.

So, I’m thinking I’d do a 20 litre tank for the meantime (until I can get some awesome 30ish litre low-boy tank). I’ve got one at home that could be set up as soon as I’m back. If I take home a big rock and sand, then I should have beneficial bacteria sorted, as well as a food source. The rock would have plants and a bit of algae and all the other good stuff you find on the rocks they like.

Other than using salt for water changes, I’d run the tank like a freshwater tank - sponge filter for filtration, freshwater light, no heater, fortnightly or monthly water changes.

I’d love to add a couple little fish if I can catch them, but I have no idea how to identify whether they’ll grow or not. Same deal with the majority of crabs (although I have ID’d a few species that would work). And unfortunately no nudibranch either… although I found the CUTEST little one last night. They’re apparently super specialist in terms of diet, and I don’t have the time to observe one for hours to see what it eats, ID it, work out how to cultivate it, and all that. 
I’m thinking maybe shore crabs could work? Or another small crab species. I found a decorator crab the other day, and OH MY GOSH was it the cutest thing I’d ever seen. If I see another one, that’s on the list of things I’d keep with the shrimp.

So, that’s the plan. I would love any advice, recommendations, or criticisms you have. I understand there’s a good chance this could be too ambitious, and the well-being of the animals is number 1 priority, so if it sounds like it’s a bad idea then I’ll just scrap it. But I’m pretty keen on finding out a way to make this work.

Edited by Crabby
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You sound like a regular Marine Biologist with that talk. Do you have access to marine water regularly? I ask because this will make water changes that much easier. No mixing just filter it through a micron filter and go. Or you can UV sterilize it. Just stay away from marinas that could potentially introduce gas and oil. Water changes you may have to experiment with. Wild saltwater critters are messy.

 

I have kept nudibranchs in marine labs before and practically all species feed on one species of coral, sponge, or tunicate. So they are not usually worth attempting. Shore crabs are also not usually fully aquatic. I am not Australian so I can’t speak to your locale. But generally speaking they need to come out of the water and don’t make good pets.

 

Decorator crabs are quite fun to keep just make sure your species stays small. Some will triple in size in just a few molts and wreak havoc on your macroalgae supply as well as any crustaceans it can get ahold of.

 

I would go ahead and get a plant light specifically as well. Algae grow very similar to freshwater plants. You may also need to fertilize them but if you use local marine water you should have all the macronutrients you need.

 

As for your fish friends I would catch them and use maybe a field guide to try and ID them as best as possible. There are a few species of fish that stay in tidepools and stay small but again I’m generalizing as my specialty is halfway across the world in the Pacific Northwest.

 

good luck and happy hunting sounds like a fun concept.

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On 1/20/2022 at 2:41 PM, Biotope Biologist said:

Do you have access to marine water regularly?

Unfortunately not, I’ll have to mix my own once I’m back home, to match the water I’m bringing home for the shrimp (if I do this).

On 1/20/2022 at 2:41 PM, Biotope Biologist said:

Water changes you may have to experiment with. Wild saltwater critters are messy.

Ah okay. This will be my first personal saltwater tank, although I’ve worked with saltwater and brackish tanks before. I’ll definitely experiment a bit to find the sweet spot for water changes.

On 1/20/2022 at 2:41 PM, Biotope Biologist said:

Decorator crabs are quite fun to keep just make sure your species stays small. Some will triple in size in just a few molts and wreak havoc on your macroalgae supply as well as any crustaceans it can get ahold of.

Yeah I had a look and it seems the species I found will stay small. Now I’ve just got to spot another one in the next 4 days… gonna keep an eye out for sure though!!

On 1/20/2022 at 2:41 PM, Biotope Biologist said:

Shore crabs are also not usually fully aquatic. I am not Australian so I can’t speak to your locale. But generally speaking they need to come out of the water and don’t make good pets.

Oops. I just assumed they’d be fully aquatic and totally forgot about my previous research into crabs. I have a feeling the ones here aren’t fully aquatic either.

On 1/20/2022 at 2:41 PM, Biotope Biologist said:

I have kept nudibranchs in marine labs before and practically all species feed on one species of coral, sponge, or tunicate.

😮 I’m so jealous. What kind of research were you doing? They’re fascinating little creatures!!

On 1/20/2022 at 2:41 PM, Biotope Biologist said:

I would go ahead and get a plant light specifically as well. Algae grow very similar to freshwater plants. You may also need to fertilize them but if you use local marine water you should have all the macronutrients you need.

The light I plan on using is one I’ve used on a freshwater planted tank before. The plants loved it. I assume I wouldn’t be able to use freshwater fertilisers though - any advice on where to look for a general marine algae & plant fertiliser?

On 1/20/2022 at 2:41 PM, Biotope Biologist said:

As for your fish friends I would catch them and use maybe a field guide to try and ID them as best as possible.

I got a pretty good video, so I’ll try to ID. They have pretty distinct patterning, which gives me hope, as fry and juvies (at least in freshwater) are usually just bland. Unfortunately the guides and resources for IDing of marine animals in Victoria are pretty terrible. 
Would adding fish mean I’d have to change much about the tank? Despite what it may seem, I’m doing my best not to over-complicate it. 😄 

Also, do you have any ideas on good things to feed? I was thinking for the shrimp I could do some frozen bloodworms? And if I added fish, then frozen cyclops, and some live mosquito larvae when weather permits?

 

Thanks for all the advice @Biotope Biologist, much appreciated. You’ve given me some food for thought.

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On 1/19/2022 at 10:20 PM, Crabby said:

 

😮 I’m so jealous. What kind of research were you doing?
@Biotope Biologist

We weren’t! At least not that I’m aware of. We had a couple of tubs that weren’t active experiments so we just kinda kept them for a week or so and set them free. We also love sea slugs and couldn’t help ourselves. 
 

adding fish shouldn’t change much about the tank. Like shrimp tidepool dwellers tend to like having lots of cover as they can be timid.

 

As for food id imagine brine shrimp for the fish or artemia they are labeled either way. And maybe diatoms? I suppose it depends on the species as some are grazers and prefer spirulina and the like. Otherwise your list looks good. You can also do morsels of clam. This is a favorite of our marine life.

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Okay, I almost ended up not going ahead with this idea. I was lacking inspiration, but today I spent a while in the tide pools and I’m back on board and excited. I saw a big school of smooth toadfish (beautiful puffer-like fish), some tiny, potentially fully aquatic hermit crabs, some cute Tasmanian Blennies, and a new fish I’m in love with - Variable Snake-Blennies (ophiclinus ningulus). They max out at 7.5cm, they’re livebearers, they all have highly variable and individual colours & patterns, and are SUPER personable and adorable. And I love them.

I’m going to collect everything tomorrow, so I think I’ll get 3-5 of the snake-blennies (so I could have the opportunity to breed in the future if I'm interested), 10ish shrimp, a few snails and sea stars, and a bunch of plants (the blennies love plants apparently).

 

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I did it! I collected the sand, rocks, plants, algae, snails, shrimp, and some special bonus creatures (which I’ll get to in a minute)! I’ve had the tank fully set up and running for about 4 days, and everything is doing amazingly. This is by far my coolest tank at the moment. I’m loving it so much. From afar it almost looks empty (aside from the awesome scape), but when you get up close, there is endless action. It is truly enamouring.

So, before I get too far, I want to quickly discuss a couple points - fish, and aquarium size. 
In terms of the fish, I’ve talked about two varieties in this thread. The first one was a species I couldn’t identify at the time, and I still don’t have a certain ID for (although I have an idea). These fish were very small, and looked almost like freshwater fish, almost the shape of an erythromicron, with a gentle yellow colour to the body and fins, and 7-9 reasonably distinct black vertical bars. I thought it would be easy to ID a fish with such distinct features. No. Not at all. I honestly poured hours into trying to figure it out (which probably wasn’t worth it), and the closest I came is that they might have been juvenile Girella Zebras. I couldn’t find any images of juveniles of this species, and I actually found literature claiming that the juveniles have much less distinct barring than the adults, but I didn’t have anything better. The Girella Zebras can get pretty big, about the size of a small Oscar it looks like, so it would’ve been very risky to collect those little fish without solid proof they would stay that size.

The other fish I found and was interested by was the Variable Snake-Blenny. This one took me under an hour to ID (thank goodness), and I was truly enthralled by. I thought it would be the perfect fish to collect. They stay decently small, have personality but aren’t constantly moving, have awesome individual patterning, and are livebearers! And they love plants too! Unfortunately, I couldn’t collect them the first time I saw them, because the tide came in so quickly. I figured I’d get them the next day, just before driving home, but no, said the universe. The tide pool had completely changed from the previous day. No longer were there millions of little water-flea-looking-things swimming everywhere, or a massive amount of seaweed and uprooted vegetation. The habitat was no longer suited to the Snake-Blennies, and so the Snake-Blennies had found somewhere else to be. Somewhere that I couldn’t find them. Yay.

Anyways, it was probably for the best, as the tank has ended up being about as full as it should be. I’ll be upgrading in the next few months to some sort of shallow 8-12 gallon tank to allow for population growth (which means next time I’m down at a beach like that, I might be getting a bit more sand, another big rock, or some extra plants).

So, to round off this post (I’ll do another one later to talk about what happened to all the critters once I got home, and share photos), let me just tell you the special species I brought back at the last minute…

Dwarf, fully aquatic hermit crabs. Mhm. Cool. So cool. The coolest. 

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