IM 50G Lagoon 'Holiday Special' Tank

[Kiiyo]

So I've been meaning to make a build thread for a while to document my tank's progress and hopefully provide someone else some guidance along the way if possible. I plan to use this also as a tank journal to hopefully make things easier to follow.


For this build, I upgraded from a standard 29G which I've had set up for almost 4-5 years, can't remember if I set it up in January of 2020 or 2021. Plenty of downs with some ups, the first 2-3 years weren't great but things stabilized over the latter 2-3. Fast forward and the tank was pretty mature at that point and served as a really helpful learning experience which I'm hoping to build off of with this new tank.

Attached are some pictures over the years with the 29G.

 

[Kiiyo]

For this new setup I was able to find a very generous member on here, @mward, who was selling their IM 50 INT Lagoon for $1! A real Christmas miracle. I made my way over to him and crammed the tank, stand, sump, and various extras into my car which all barely fit.


Everything was well loved but required a bit of cleanup so I spent the next couple of weeks cleaning the tank, replumbing, and preparing the new space for the tank. Thankfully I was setting the tank up in a different space than my old one so I wasn't rushed in that sense.


Previously I had run an Aquaclear 70 on my tank and have never had a sump and never set one up. In all honesty I wasn't intimidated, but looking back I think I should have been. It was more work than I had considered and there was a lot to set up since I needed to replace basically everything that was involved with plumbing. After it was all said an done, I don't think I'd ever go without one again and I look forward to setting up my next sump. Putting all the plumbing together wasn't bad, it was gathering the correct supplies that was the tough part.

 

[Kiiyo]

Now that I had everything fitted and connected, time for water! One piece of advice I'd give to anyone doing this for the first time, make sure you test your overflow area is water tight first. I unfortunately filled the tank area with water before I found a leak in a couple of my bulkheads. FORTUNATELY, they just weren't tight enough and that fixed the issue. However, I had set the tank up in it's final spot up against a wall and it was a PITA to tighten these bulkheads.

This is what we have right now under the tank. The cabinet doesn't have much space and my cable management is non existent right now but I plan to fix this up when I have the time. I'm struggling to figure out where to put the power strip, any suggestions are welcome. To those of you who can hide all your cables and make nice controller boards, my hats off to you.

 

[Kiiyo]

Currently

 

[Kiiyo]

New inhabitant to the tank. Black leopard wrasse per the suggestions of a couple over on the wrasse lovers thread.

She's eating well and getting along with everyone else.

Also picked up a kamoer f1 to help with dosing AFR.

 

[Kiiyo]

Recently picked up some sps frags. They're all named pieces, but I'm only aware of the large one on the left. If someone could help me ID any of these, that's be appreciated.

During transport the large one had a piece break off and I put it on a plug so hopefully it survives

Images

 

[Kiiyo]

Great tragedy today as I learned my leopard wrasse is bullying my mandarin dragonet. I noticed the mandarin would only come out at night when the wrasse went to sleep and couldn't figure it out until now.

Not sure what to do, but I should probably make a decision so the mandarin doesn't starve since it's hiding all day. When I've seen him, he doesn't look skinny so that's nice but I don't think I can just leave them long term.

Any advice or input would be appreciated.

 

[Kiiyo]

Rehomed my black leopard and picked up a bangaii and Hector's goby. Everyone is doing well. Swapped a malfunctioning nero 5 for the 6095 I won from a monthly giveaway that was done on R2R earlier this year. Man that thing seems way stronger than what it says it's rated for.

 

[Austinsdepenbrock]

Looking good!

 

[Kiiyo]

Recently neglected the tank and had a spike in phosphate I'm currently trying to get under control. I also unclogged my main drain which was completely blocked by a trochus snail which lead to a loud partial siphon from my secondary drain.

 

[Kiiyo]

After an ugly ulva and hair algae outbreak, things look to be improving. I added 1/4 a cup of gfo in a filter bag in my sump and manually removed a lot of the algae. In addition, I restocked some clean up with 2 astrea and 2 margarita snails along with an emerald crab. They already made great work towards clearing my rock of algae and I hope to see everything clean again in a few weeks. My po4 dropped from 0.27 to 0.17 in a little over a week and I'm looking to have it below 0.1 in some time.

Overall things are looking up from where they were. My issue was, and has from time to time, not consistently testing and not fixing things when I first see them crop up but instead letting them get worse. Water changes were never and issue but I know I need to test to really understand what's going on. Here's to maintaining a better standard of testing.

 

[Kiiyo]

I've been trying to be more consistent and have been battling ulva and hair algae for what feels like much longer than the month or so it's been going on. Manual removal has helped with the ulva, but now I think I need to target the hair algae as that's become more prevalent.

Current tank shot, it really hurts to see that I've lost all my acros. Financially it doesn't feel good, but I definitely felt more of an impact confidence wise. I thought I was coasting and had things down but that wasn't the case.

I haven't been able to pinpoint what exactly caused the die off, but my guess is nutrients. It wasn't all at once and many pieces browned out before bleaching. I prolonged my water changes of 5 gallons to every 3-4 weeks rather than the 2 week intervals I had performed them. Simultaneously, I let my skimmer go 6-8 weeks between cleanings. This led to my nitrates (8/30 - 11/9, 0 to 19.1) and phosphates rising(8/17 - 11/9, 0.08 to 0.25). I believe my acros began to decrease their consumption of alk and caused this to rise as well
(10/18/25 - 11/28/25 - 1/24/26, 8.3 to 9.1 to 9.8).

I wasn't happy with my low nutrient numbers and I foolishly chased numbers thinking I knew better than the collective wisdom of the reefing community.

I'm looking to get rid of most of the algae, get back into a schedule, and keep things stable before I try sticks again.

On a positive note, I didn't see any other significant die off from other coral during this time.

 

[Calmwaters]

I've been trying to be more consistent and have been battling ulva and hair algae for what feels like much longer than the month or so it's been going on. Manual removal has helped with the ulva, but now I think I need to target the hair algae as that's become more prevalent.

Current tank shot, it really hurts to see that I've lost all my acros. Financially it doesn't feel good, but I definitely felt more of an impact confidence wise. I thought I was coasting and had things down but that wasn't the case.

I haven't been able to pinpoint what exactly caused the die off, but my guess is nutrients. It wasn't all at once and many pieces browned out before bleaching. I prolonged my water changes of 5 gallons to every 3-4 weeks rather than the 2 week intervals I had performed them. Simultaneously, I let my skimmer go 6-8 weeks between cleanings. This led to my nitrates (8/30 - 11/9, 0 to 19.1) and phosphates rising(8/17 - 11/9, 0.08 to 0.25). I believe my acros began to decrease their consumption of alk and caused this to rise as well
(10/18/25 - 11/28/25 - 1/24/26, 8.3 to 9.1 to 9.8).

I wasn't happy with my low nutrient numbers and I foolishly chased numbers thinking I knew better than the collective wisdom of the reefing community.

I'm looking to get rid of most of the algae, get back into a schedule, and keep things stable before I try sticks again.

On a positive note, I didn't see any other significant die off from other coral during this time.

Losing corals is painful! Hopefully you don't lose anymore.

 

[Kiiyo]

Losing corals is painful! Hopefully you don't lose anymore.

Me too, consistency and diligence pays off in this hobby. Those are the keys words I'll remind myself of moving forward.

 

[Kiiyo]

I've been following through with my goal of weekly 10% water changes and as a result I've noticed my nutrient levels have begun to come down and my nuisance algae appears to be less prevalent than before. I've also seen my ulva diminish and had an uptick in GHA, but still a reduction nonetheless.


Additionally, I set up a refugium using chaeto and a spare led I had lying around that's currently on a 12 hour reverse photoperiod. I didn't see chaeto growth for a week or so at the beginning, but it's been booming ever since.

This is after about 4 weeks of growth and I threw out the majority of the chaeto last weekend.

This leads to the most recent news. I'm trying my hand at acros again after picking up some beautiful pieces from a local reefer.

 

[Kiiyo]

Took some pictures the other day.

Still battling ulva and hair algae with some success? Recently deployed GFO in a media bag and it's brought po4 down from 0.25-0.29 to about 0.17 in 2 weeks, so we'll see how that goes. Also still running chaeto with moderate success, harvested twice in 2 months.

Really seems like you never want to let algae get a foothold in the tank, keeping it at bay appears to be infinitely more manageable than removing it once it's gotten in.

We continue with the fight on.

I've wondered if a short term tang rental would help, but that presents its own set of issues. So I'm leaving it as a less desirable option for later down the road.

 

[Gumbies R Us]

Took some pictures the other day.

Still battling ulva and hair algae with some success? Recently deployed GFO in a media bag and it's brought po4 down from 0.25-0.29 to about 0.17 in 2 weeks, so we'll see how that goes. Also still running chaeto with moderate success, harvested twice in 2 months.

Really seems like you never want to let algae get a foothold in the tank, keeping it at bay appears to be infinitely more manageable than removing it once it's gotten in.

We continue with the fight on.

I've wondered if a short term tang rental would help, but that presents its own set of issues. So I'm leaving it as a less desirable option for later down the road.

Best of luck on the gha and ulva issues!

 

[tbrown]

I've fought that Ulva in two tanks now. It's not a fun one. Hermit crabs and emerald crabs did the best for me with it.

 

[tbrown]

So long term, a 50 is going to be too small but my Tomini attacks my GHA pretty decent. They also stay smaller and are ok for a 65-70 gallon tank. I've had mine for around 5 years. Started in a 75, up to a 125, and now back to a 70 and he's still around 3.5".

 

[Kiiyo]

So long term, a 50 is going to be too small but my Tomini attacks my GHA pretty decent. They also stay smaller and are ok for a 65-70 gallon tank. I've had mine for around 5 years. Started in a 75, up to a 125, and now back to a 70 and he's still around 3.5".

My LFS gets them small so I've been thinking about it more and more. I'm hoping that nutrient export can do the trick as I have a strong opposition to putting fish in too small tanks.

For example, my Possum wrasse is said to be okay in a 20g, which it definitely can live in, but it uses all of the space in my 50g. I can't imagine shoving a Tomini in a 50g for any extended period.