Fishtank Coffee Table / Glass-Bottom Effect

[mxracer19]

Hey all,

As my first post let me first introduce. My name is Matt and I'm somewhat of a beginner in this hobby. I've been successfully keeping a 20g Long reeftank for a little while now, and now that I'm moving into a larger apartment, Ive decided to expand with a second tank.

Necessity being the mother of invention, not only was my new apartment lacking the second tank I so desired, I was also wanting for a new coffee table to match our decor. With these desires in mind, I set about to build my first tank. You guessed it...a tank inside a coffee table.

As you've all seen, looking down through the surface of water gives skewed views. I therefore decided that for this tank to have the view desired, the water level must be flush against the surface of the glass surface. To facilitate this, the tank itself is in essence a glass box, with a sump tank hidden inside the storage portion of the table being used to control water levels. One bulkhead in the side of the display tank will provide the return. Two bulkheads through the top section of glass (the display portion as well as the surface of the coffee table top) will allow the water level to rise higher than the viewing plane. Basically, water level in the DT will rise until it meets the display glass, and when it cannot proceed any further it will escape out through vents in the top. These overflow vents span from the display surface to the sump section of the tabletop, and then down through the tabletop into the sump tank.

From here, water will be cycled through my protein skimmer, released into the refugium (DBS, Macro-algae), and from there released into the pump chamber where it will be pumped back to the DT via my Rio HF8. At 0' of head, this pump is rated at 660gph. Being only 40 gallons in volume with a max height of 1', my return pump is the primary source of water circulation.

Potential problems include aeration, feeding, and access to the DT.

Aeration will be accomplished via the protein skimmer and airstones placed in the refugium.

Feeding will be accomplished via an isolated feeding chamber inline with the retun pump. A pelican case, drilled for bulkheads at either end, will be plumbed parallel to the return line, after the pump but before the tank, and isolated from the circuit with ball valves. At the time of feeding, food will be placed in the case and the case sealed. The ball valves for the case line will be opened and the straight-through line valve shut, thus diverting water from the straight-through line, through the case, carrying food to the DT. After feeding, the straight-through line valve will be opened and the case-valves closed, restoring normal flows to the tank.

Access to the DT will be infrequent. Due to the requirement of higher-than-normal water levels, a seal between the display tank and display glass surface must exist....and THIS...is where I've hit a bit of a roadblock. My original plan is to grease the edges of my display glass(DG) with silicone grease, lay a bead of silicone sealant around the perimeter of the DT, rest the DG in place until the silicone sealant cures, and then hopefully, the silicone grease will allow the removal of the DG while still leaving a smooth silicone surface to act as a seal for future removal of the DG. By my calculations, the weight of the DG will provide 1psi of force over the seal and what I'm HOPING...is that this will be enough to seal the display glass (DG) to the DT, much the same way as a diver's mask seals to his face using a silicone skirt, and thus permitting the extra 2 inches of water height in my twin overflow drain vents!...We shall see... At this current stage of the build, the table is complete. The glass is in place. I am awaiting the hole saw in order to drill the tank, and once that is accomplished I will plumb, fill, and test the system.

I am making a request for advice on sealing the display glass to the display tank in order to keep water INSIDE the semi-closed system, while still maintaining SOME level of accessability to the display tank in order to add/remove inhabitants and alter aquascapes/perform general maintenance.

Thanks in advance,
Matt

[Dragonist]

This sounds like a difficult build. Are your referring to sealing the top glass? I would recommend not sealing it. Reason I state is because that seems to be the least difficult way to access the tank. Also what do you plan for lighting? May be you could use leds mount on the four corners of the tank. Or possibly purchase a retro-fit kit and mount the blubs on the edges of the enclosedure. Are your going to do reef or fowlr(fish only with live rock)? Do you plan to have the tank viewable from the top of the coffe table or merely the sides?

[mxracer19]

The top surface of glass must be sealed to the tank itself because the water level will be above that pane of glass in the overflow vents...I might not have been as clear as I couldve been with the description.

If you open the attachment with the picture of the finished table you'll notice a hole cut away out of the sump area...This 30" x 5" slot is going to be for a T5 fixture, with LED's in the corners of the tank for spotlighting. I plan to keep some fish with easier-to-keep coral varieties. I may use food-grade strip caulking to seal the glass, but that has yet to be determined. As an update, today I recieved the holesaw from glass-holes.com. Great guys to order from, I highly recommend them.

The tank will be viewable primarily from the top as I plan to raise the water level to the surface of the glass top to allow for the clear view one attains from glass-to-water contact.

I'll post more pictures when I can!

Thanks,
Matt

[Loverotties]

Boy is it going to be fun trying to get anything out and also clean things and glass.

[mxracer19]

Alright guys, new ideas. I've decided I'm going to give the strip/bead/rope caulk a shot at sealing this puppy up. My only worries are toxicity issues with chemicals leaching out of the seal. As long as this doesn't happen to a toxic level we should be good.

Secondly, I've attached better pictures...One from before the paint and one after, both showing construction, and a third displaying the overflow holes in the display glass that have yet to be plumbed.

Third, the fit between the wood tabletop and the display pane of glass is a bit tight so I'll be removing the tank and relieving some of that wood to aid in clearance issues. This, followed by a repaint of some sections, shouldn't take very long.

The pumps are inbound via mail and Home Depot is open for a plumbing shopping spree tomorrow.

Goals for tomorrow:

Drill the hole in the side for the return.
Plumb the entire system.
Successfully seal the top after relieving wood.

[Loverotties]

Looking good!

[Dragonist]

Originally Posted by mxracer19

The top surface of glass must be sealed to the tank itself because the water level will be above that pane of glass in the overflow vents...I might not have been as clear as I couldve been with the description.

If you open the attachment with the picture of the finished table you'll notice a hole cut away out of the sump area...This 30" x 5" slot is going to be for a T5 fixture, with LED's in the corners of the tank for spotlighting. I plan to keep some fish with easier-to-keep coral varieties. I may use food-grade strip caulking to seal the glass, but that has yet to be determined. As an update, today I recieved the holesaw from glass-holes.com. Great guys to order from, I highly recommend them.

The tank will be viewable primarily from the top as I plan to raise the water level to the surface of the glass top to allow for the clear view one attains from glass-to-water contact.

I'll post more pictures when I can!

Thanks,
Matt

My thoughts are how hard it will be to work in the tank. Thought about drilling the holes down lower and making it where you could open the top pane?

[quader94]

theres something similar to this at one of my LFS.

they have a glass top
and then theres a gap of about 3 inches and then theres a tank similar to yours
then the plumbing on the side

[mxracer19]

Originally Posted by Dragonist

Thought about drilling the holes down lower and making it where you could open the top pane?

I have, and that's my backup plan. The original goal was to run the water flush with the glass to give that "underwater dive-mask" view. We'll see how many problems this causes as the tank progresses and alter plans as need be.

[mxracer19]

Update:

I assembled some of the system utilizing both plumber's putty and strip/rope caulking as sealants. Both failed. As water levels rose to reach the bottom of my drain, I hadn't counted on them sealing off. This created an air pocket, and as water rose further, this air pocket pressurized, and blew out my otherwise semi-water tight seals. Therefore, holes were drilled around the two overflows where they contact the glass to allow this air pocket to discipate.

Additionally, I have decided that putty and caulk will not be suficient to seal the system. I am going to attempt my original idea of greasing the display pane with silicon grease and just silicone-sealing it on on. Hopefully the grease will permit a somewhat easy removal, and at least I know it's non-toxic.

Despite not having a perfectly water-tight seal during initial tests, due to surface tention I managed to get pictures of what the water level looks like up against the glass. It looks awesome and in one picture I left a large bubble to depict the differences between how the water looks against th glass and how difficult it is to see through the surface when it is not against the glass. I WILL...get this project to work...

[gouch]

this sounds really cool.....after looking at your schematic i think you can make it work........but it not gonna be easy

here what i used to silicone in my baffles. "Dap" aquarium. its made for this.



i would consider using somthing like "weld on" (check melevsreef.com in the DIY page) and then silicone on the inside and outside. then build your coffee table with a molding that covers the ugly silicone mess just my 2 cents what ever you do i hope it works im along for the ride.

[mxracer19]

Hey thanks man. As a quick update Im laid up after hernia surgery so I have plenty of time to sit around waiting for things to dry. This morning I tested the silicone seal. The silicone grease did not make the top any easier to remove, however after 5 minutes of water flow the glass did separate from the tankwalls. I feel this is because I only let the silicone set up for 3 hours. Had I let the silicone sealant cure for the full 24 hours I am 100% confident that the top would've stayed sealed. Removal was quite easy with a razorblade, but after removing the top the interior area of the silicone was still liquid, hence the compromised seal.

The vent holes drilled around the perimeter of the drains did their job by venting air and allowed a complete fill to the glass surface, and the flowrate is sufficient to handle a garden hose without both drains developing a siphon. Just incase, I plan to tap one of the cross-drain pipes in the top for a piece of clear tubing to use as a breather, routing the open end to a point above my sump. This airvent will allow one drain to vent without developing a siphon, yet in the event one is created, it will overflow into the sump.

The number of times that the top needs to be rmeoved should be fairly infrequent. After initial setup, I'll allow the tank to cycle for 6 weeks so for that period of time nothing will be needed. After those 6 weeks I'll open the tank to stock it (After saving for 6 weeks ), leaveing the top off for a day or two utilizing an overflow box, and after I am happy with placement, I will seal the system and charge the drains. While the top is off, flow can be maintained via one powerhead inside the tank, or through a custom removable overflow box designed to facilitate operation without the display glass drainage system in place..

Overall, I think I'm nearing completion.

Thanks,
Matt

[gouch]

ok im liking this build. very unique......hope it works for you

[D.J.]

WOW..........thats all i can say........i have always wanted one of these...but could never afford one and seeing you build one just really blows my mind.......

GREAT WORK............i cant wait to see more of this thing........

i have a question..that has probably already been answered....how do you access the tank witht he sealed top? in case you have to get int here for a dead/dying/sick fish or to add livestock and all?

[mxracer19]

That's the situation Im trying to workout. My original plan was to create a seal with silicone simply by the weight of the glass top, however this proved to be a failure. So far the only solution tried and true is physically sealing the top with silicone. To get into the tank, you'd have to cut the top off every time. It's going to be a pain in the butt but I'm thinking that if I can cut a square opening somewhere in the corner of the glass, then from the inside I can place another piece of glass with a seal, using the water pressure to hold it in place. However, I'll most likely just end up raising the tank 1/4" in it's stand to expose the edge of the display glass in order to make it easier to cut the top off when I have to get in. To keep the inhabitants alive while the sealant recures after resealing, I'll just use the intank powerhead to circulate water with an airline to provide aeration. Folowing cure, air will be purged and the main pump restarted.

ALL THIS HASSLE....is the primary reason I plan to raise the tank as an invertebrate/zooanthid/mushroom display with LIMITED fish. Since I'll have a relatively large sand bed in comparison to the overall depth, I plan to do a slightly sloping rockscape to capitalize on the end-lighting. This should cast unusual shadows and allow for some interesting lighting conditions.

I hope to circumvent problematic additions witha tonnnnn of planning and research...so that hopefully once I've added things, I won't need to mess with it much....we shall see!

Thanks for all the compliments
-Matt