Fluval M90 Conversion Tank Build

Kerinin

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I had to tear down my Fluval M90 a few years ago. Now I'm setting it up again and I'm planning to learn from my mistakes the first time around.

My plan is to take it slow this time - I'll be following a lot of the advice from the BRS/Hybrid video series, with the intention of transitioning to the Triton system as the tank matures. The first step is modifying the tank - the Fluval M90 is a 36g AIO that comes with a cabinet. I'm planning to drill an overflow, modify the cabinet to be taller, and add a ~14g sump with a refugium.

I successfully drilled the holes and removed the internal compartments this past weekend - the part of the conversion I was most worried about messing up. Once that was done I removed the internal dividers and did a preliminary scrape & clean:




The tank cleaned up really well - better than I had hoped. Here it is with the overflow and return hardware installed:

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I'm currently in the process of painting the back and bottom surfaces black - applied the second coat today and I'll see how it looks tomorrow, hopefully won't need a 3rd.

Next step is to prepare the cabinet for the sump, which should arrive Thursday. I'm planning to remove the middle shelf and replace the doors with full-height panels.
 
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Kerinin

Kerinin

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Finished back-painting the glass, and removed the doors & intermediate shelf from the cabinet. I'm still thinking about what to replace the cabinet doors with - they only extend halfway down. I may just add a slab of marine plywood and a new laminate surface.

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WIReefer

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Looking great! My first tank was the fluval m90 but the tan edition. Awesome tank!
 
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Kerinin

Kerinin

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Coming along! Sump is installed and plumbed. Currently a few days into the live-rock cycle in the basement, will probably transfer to the tank in a day or two. Still working on fabricating some new (larger) cabinet doors. Found an old table at the local Habitat for Humanity ReStore that I'm going to use for the panels - waiting for a drill bit to install the hinges.

Current equipment list:
* (2) Sicce Syncra 1.5 return pumps plumbed in parallel to return nozzles. One is routed through a manifold with two ports for (future) reactors.
* (2) WAV powerheads - probably vastly oversized, but I'm shooting for a high-flow, bare-bottom tank.
* AquaMaxx ConeS HOB skimmer that I've pulled out of the HOB body. Curious to see how this goes - may end up needing to buy a new skimmer.
* Apex El, currently in the basement monitoring the LR cycle.

I should have a couple peristaltic pumps arriving from China in the next couple weeks, which will be part of a DIY dosing, ATO and automatic water-change system I'm building.

Water-testing the plumbing work:

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Kerinin

Kerinin

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Moved the cycle into the tank, turned on the skimmer. The overflow is more sensitive than I expected - there's a very narrow line between too much flow and gurgling and not enough flow and going down the emergency drain.

4970FA99-881F-4BD9-BA02-EF193EBDD0E0_1_105_c.jpeg
 
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Kerinin

Kerinin

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Finished the cabinet doors - water still pretty cloudy. Started the skimmer yesterday and it's pulling a bit of sludge but not too much (considering the turbidity).

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I couldn't find the power for my ATO and naively pugged in the power supply to a Gyre pump I'm, not using. Turns out the ATO expects 12V and the pump was providing 24V, so I may be without ATO until the peristaltic pump arrive. They're currently clearing customs, so I'll just have to top off manually for a week or two.

The overflow is louder than I had hoped, mostly caused by gurgling on the tank side. I'm working on some plans to fabricate a wider weir - my theory is that doubling the inlet size will reduce the velocity of the flow and hopefully result in less noise as the water makes its way from the weir to the manifold. I thought about replacing my overflow with a larger version, but I'm kind of committed to two drain pipes and all the larger overflows are for 3. Sad times.
 
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Kerinin

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Coming along slowly - still seeing a lot of ammonia and the water hasn't quite cleared yet. Skimmer is still on, but doesn't seem to be pulling out too much - I think I'm going to replace it with a proper in-sump skimmer (I'm using the inside portion of a HOB skimmer).

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Kerinin

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Pumps arrived! Now I just need to get them to run. Also extend reef-pi to support them, no big.

IMG_1160.jpg
 
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Kerinin

Kerinin

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Did some testing and calibration - pumps are perfect! Dialed in to the speed they'd need to run at to do a 10% weekly water change they're effectively silent.

Current plan for these three is a combined ATO and water change system - one pump for NSW, one for saltwater, one for RODI, and one for discard. I was originally planning to buy some water level sensors, but I accidentally fried my Osmolator by plugging it into twice the voltage it expected so I'm hoping I can salvage the sensors it was using and connect them to the arduino.

If this all goes well I'm planning to get another 2/4 for dosing. Still trying to decide if I want to transition to Triton or just supplement Ca/Alk.

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Kerinin

Kerinin

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I've been trying to reduce the noise coming out of the overflow since I set the tank up. The original design was to use an external overflow and a Herbie drain. This worked OK-ish - the water level in the overflow box we SUPER sensitive to adjustments to the valve but when it was dialed in the overflow box was pretty quiet.

The problem was that the internal box was constantly making splashing sounds. My first thought was that I had undersized the overflow box for my return flow, so I fabricated a new overflow box (sometimes it's nice to have a CNC machine in the garage):

Screen Shot 2020-08-15 at 12.39.09 PM.png


This increased the area of the weir by about 2x, keeping everything else roughly the same as the box I started with. The new internal box helped, and the flow into the box was more consistent it would have been a good solution. But the flow isn't consistent - my power-heads are generate a lot of turbulence in the tank, and the surface waves often cause the overflow going into the internal box to increase enough to cause splashing again.

I eventually settled on yet another modification to the overflow - this time increasing the height of the external box to be level with the top of the tank. This allows me to increase the height of the emergency standpipe and raise the water level to be about a half-inch below the tank level. So far it's working pretty well - the tank is silent and AFAICT all my acrylic welds are holding water. Will have to keep an eye on the seams to see if I start getting salt creep.

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nickng

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I've been trying to reduce the noise coming out of the overflow since I set the tank up. The original design was to use an external overflow and a Herbie drain. This worked OK-ish - the water level in the overflow box we SUPER sensitive to adjustments to the valve but when it was dialed in the overflow box was pretty quiet.

The problem was that the internal box was constantly making splashing sounds. My first thought was that I had undersized the overflow box for my return flow, so I fabricated a new overflow box (sometimes it's nice to have a CNC machine in the garage):

Screen Shot 2020-08-15 at 12.39.09 PM.png


This increased the area of the weir by about 2x, keeping everything else roughly the same as the box I started with. The new internal box helped, and the flow into the box was more consistent it would have been a good solution. But the flow isn't consistent - my power-heads are generate a lot of turbulence in the tank, and the surface waves often cause the overflow going into the internal box to increase enough to cause splashing again.

I eventually settled on yet another modification to the overflow - this time increasing the height of the external box to be level with the top of the tank. This allows me to increase the height of the emergency standpipe and raise the water level to be about a half-inch below the tank level. So far it's working pretty well - the tank is silent and AFAICT all my acrylic welds are holding water. Will have to keep an eye on the seams to see if I start getting salt creep.

IMG_6970.jpg
IMG_1154.jpg
Hi, just stumbled on this. Do you happen to know what is the thickness of the glass used on the Fluval M90?
 
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