Timfish

Looking good!

Dinner 😄

That's a really cool looking crab.  It's left claw is definitely used for grabbing and crushing though and it's right claw doesn't have any "spoon" shape to it.  Looks like your ID is right. 

  Just because they don't have a brain doesn't mean they don't have a social life and feelings.  Look at what's been found with their cousins:

It's funny how self-conscious some people can get sometimes when you talk about them.  🤨

Multiple people are breeding the Royal urchin and I have seen them available form Biota.

It might be getting ready to spawn.  It might be pulling surface stuff off to eat but I think the feeding behavior is more likely just instinct.  Is that an area that doesn't have any surface currents?  FWIW, if the spawn is yellowish or orangish it's a female releasing eggs, if the spawn is white it's a male and the spawn is sperm.

Any issues yet with the corals from the drop in salinity?

Hmmm, no one thought of a frigid water reef forum. 🙃  Pretty cool stuff!  But I want to know where the cold weather is you should have brought back with you?!

Welcome!  Things have changed a lot and our understanding of the microbial processes has increased significantly parralelling the discoveries with microbiomes in humans and in soil.  This is a bit of a data bomb but here's a list of links you might find informative.  Don't feel like you need to understand how it all works together, not even the scientists doing the research understand all the intricacies of reef ecosystems and they are finding new stuff almost daily.  But do go back and reread and rewatch stuff periodicly, when I do I'll be reminded of stuff I forgot or see new connections to stuff.  Enjoy!

"Coral Reefs in the Microbial Seas" This video compliments Rohwer's book of the same title (Paper back is ~$20, Kindle is ~$10), both deal with the conflicting roles of the different types of DOC in reef ecosystems.  While there is overlap bewteen his book and the video both have information not covered by the other and together give a broader view of the complex relationships found in reef ecosystems
https://www.youtube.com/watch?v=-R2BMEfQGjU

Changing Seas -  Mysterious Microbes
https://www.youtube.com/watch?v=c7hsp0dENEA

Microbial view of Coral Decline
https://www.youtube.com/watch?v=NAD26LGERj8

Nitrogen cycling in hte coral holobiont
https://youtu.be/DWItFGRQJL4

BActeria and Sponges
https://www.youtube.com/watch?v=-oLDclO7UcM

Maintenance of Coral Reef Health (refferences at the end)
https://youtu.be/dGIPveFJ_0Q

Optical Feedback Loop in Colorful Coral Bleaching
https://youtu.be/oadKezUYkJE

DNA Sequencing and the Reef Tank Microbiome
https://www.youtube.com/watch?v=ghxVSmLhxUg

Richard Ross  What's up with phosphate"
https://youtu.be/ZRIKW-9d2xI

15 Answers
https://www.youtube.com/watch?v=pqTuQDzjlv4

I'm guessing from the speed the algae came back it's green water and not hair algae all over the substrate.  If so, first thing I'd try is a cheap 9 watt or 13 watt submersable UV sterilizor from walmart or amazon.

That last pic looks like there might be "spoons" at the tips of the claws like mithrax carbs.  It is really cool stuff!

SOunds like it's omnivorus.  At it's size it doesn't seem like it would be much of a threat to fish.

That's a lot of crabs!

Any update?  Did you leave it or take it out?

(I've never done that! Honest! )

Interesting, can't say I've ever seen one like that.  The two things I would look for are the back or last pair of legs and the shape of the claws.

If the back pair of legs are shaped like the other three pair and not wide and flat like a blue crab's back pair used for swimming it's not a fish preditor per se.

If the claws have flat or spoon shaped tips like and emerlad it's a herbivore.  If the claws are scissor like with flat edges that line up evenly (like a thin stripe hermit) it's also a hermit herbivore.

If the clwas are nobby and have pointy ends they're used for grabing and crusing and while not a preditor of fish like blue crabs they will be opportunistic if they corner a fish in a crevis or hole.

That ATO looks nice and a cover is a big plus.  Your dimensions look like a generic 10 gallon tank would fit and be cheaper even if you have to get or cut an acrylic a cover for it.

Cryptic sponges are easy, jsut get some live rock from Gulf Live Rock, Tamp Bay or KP Aquatics.  Tyree has a couple ebooks out you might be able to get ahold of.  He demonstrated some prescience advocating sponges back in the 90s.  Work by de Goeij showed cryptic sponges remove the labile DOC that can have serious ramifications for corals 1000X faster than the bacterioplankton (which is only partially removed by skimmers).  You can still put a small light to establish a day/night cycle but it wouldn't have to be nearly as bright as what you would need for macro algae.

You can probably get several in a package and let your urchin decide for itself what it wants to wear any particular day (or evening ;D).

I wouldn't bother with cheato, grow cryptic sponges.  Sponges are essential recyclers on reef systems.  Macro alga on the other hand compete with corals and while chaeto isn't as bad as turf and hair alga for releasing the DOC that causes issues with corals it still releases some.

Will a bucket or tank sit next to your sump?   FWIW I always have issues ATO issues with sensors, pumps and with float valves if left too long with out maintenance.  I used to wait until they had issues to bother with them and gone years with some but it's less hassle to plan on a good cleaning every six months to a year, the amount of ambient light can be a variable too

Your urchin is a caribbean species generally called a pincushion, collector or pink short spine.  It's likely Lytechinus variegatus and has a range of colors from green to pink to white.   They can carry a lot of stuff but from what I've seen there does seem to be individual preferences which is curious as thy don't have brains, at least not a brain as as we think of it.  You can get hats for them online.

Everything's looking good!  Nice to see your fife shrimp isn't shy and hiding a lot like some I've seen.

If you have any signs of algae growing on the rock I'd add one.   Tuxedo, Royal or Caribbean short spine pink or green or white would be good choices.  Tuxedo's are captive raised but obvioulsy will be more expensive.

Interesting, and cool even if it isn't something you want long term.   The last post by SDE1500 in the link you posted shows a turf algae, definitley not the same thing as the other photos or yours, he may have had the "dandelions" initially on the rock but there would have been a succesion of different algae.  I can't say Ive ever seen it on any rock which tells me it either short lived and rarely survives in aquaria or has very specific requirements and is easily outcompeted by other organisms.  I'd leave it but if it worries you, you can try some H2O2 in a syrenge and apply some at the base.

18 hours ago, ckyuv said:

Sooo, here I go changing my game plan already. . .

😱

Just for the record I never have to change any plans I make for one of my tanks. 😏

You didn't mention anything about algae eaters but I would go ahead and add an urchin and some hermits, it won't hurt to get ahead of the uglies and they don't need much attention.