Help Designing a custom glass lid for UNS 90u

[tsmith_old_guard]

I am putting a UNS 90u in my office. I need a lid for this tank to minimize evaporation. This will be a fully planted shrimp tank with some nano fish. The lid will rest on acrylic clips inside the tank. I went with a three-piece lid design. The front two glass pieces will be hinged like your standard glass aquarium lid. I was going to leave a 2.5-inch gap at the back of the tank and put on a plastic backstrip, again, like most glass lids. I decided to go ahead and have a third piece of glass cut to fill this void for now (mainly for looks). Filtration is a single Biomaster 600 as the canister filter. I am having the front corners cut out of the first piece of glass at 2.5-inch x 2.5- inch to have an opening for the stainless steel lily pipe inlet and return (adjacent to each other). I wanted to see if anyone had feedback or design critique. I made all measurements from the interior of the tank with the clips on both sides, gave an 1/16-inch cushion on that measurement and another 1/16-inch tolerance in the final glass measurements. This should give me 1/8-inch margin for error. (I also have stainless steel clips I can use to give me another 1/8-inch cushion if needed. Initial concern is if the front cutouts are large enough for the Lily Pipes. Thoughts on the proportions of the two main lids? I will have a Chihiros wrgb pro 90 mounted on the rim. I worked with chat GPT to adjust the tolerances and give scaled drawings. Any feedback is appreciated. Aquarium Design Group (ADG) referred me to their glass cutter they use here in Houston. I called and got a quote for a two-piece lid with two cutouts for $150. That is much better than the quotes I get for a custom Lexan lid! Measurements and Drawings below. Thanks again for the input! I want to "kick the tires" before I order the lid.

Custom Aquarium Lid – Design Version 3​

Tank Interior Opening Dimensions (including lid clips):
Length: 34 3/16 in
Width: 20 15/16 in

Finished Glass Assembly Size (with tolerance):
Length: 34 1/8 in
Combined Width: 20 7/8 in

Piece Dimensions​

Piece	Position	Dimensions	Notes
Piece 1	Front	34 1/8 × 6 in	Two front corner cutouts 2.5 × 2.5 in nominal, inside radius 1/2 in
Piece 2	Middle	34 1/8 × 12 3/8 in	Rectangular panel
Piece 3	Back	34 1/8 × 2 1/2 in	Rectangular equipment strip

 

[tsmith_old_guard]

I was looking at the F-Zone Lily Pipes when sizing the cutouts.

 

[Koan]

I decided to go ahead and have a third piece of glass cut to fill this void

Will this be a low tech or high tech tank?

If you're injecting co2 into a non open-top tank, you have to create specific opportunity for a lot of gas exchange with the room.




This means either an HOB filter, actively driving oxygen from the room down into your tank, or a lot of gap around your lid, or a lot of holes in your lid.

If you don't make sure there's access to adequate oxygen over the water surface, you will collect CO2 at the surface.

This will suffocate your fish and shrimp Ask me how I know

 

[techman81]

Will this be a low tech or high tech tank?

If you're injecting co2 into a non open-top tank, you have to create specific opportunity for a lot of gas exchange with the room.

View attachment 15218


This means either an HOB filter, actively driving oxygen from the room down into your tank, or a lot of gap around your lid, or a lot of holes in your lid.

If you don't make sure there's access to adequate oxygen over the water surface, you will collect CO2 at the surface.

This will suffocate your fish and shrimp Ask me how I know

Yep. I used to keep a lid on my farm tank. When I removed the lid, I had to crank up the CO2 injection to equal the same ppm.

 

[tsmith_old_guard]

If you don't make sure there's access to adequate oxygen over the water surface, you will collect CO2 at the surface.

This will suffocate your fish and shrimp Ask me how I know

Thank you, this great feedback. I am planning to use a lily pipe with a surface skimmer on the outflow to help with surface biofilm and gas exchange. But I did not think about a layer of off gassed CO2 displacing oxygen between the lid and the surface of the water. I made that third piece removable just in case I did not have enough room for gas exchange. I hadn't thought about a blanket of CO2 the way you described it. I had thought about putting a small air stone on a timer to run opposite of the lights/CO2 for when the plants switch from photosynthesis to respiration and start using oxygen. This was to be a backup since I would not be in my office during this time to notice a problems in the tank. Did you lose a batch of fish and shrimp?

 

[tsmith_old_guard]

@Koan I double checked the measurements. I will have a 3/8" gap all around the lid, and single 4" x 3" cutout for lily pipes. I am also planning to run surface skimmer on the lily pipe out flow. Some initial googling seems to suggest this is a sufficient gap for gas exchange. Does this seem sufficient? (yes, this will have CO2 injection). I can always add surface agitation via skimmer and/or lily pipe outflow elevation, but that wouldn't help if a 3/8" gap around the entire lid would be insufficient for gas exchange. Final thoughts? Thanks again for all the feedback.

 

[Koan]

also planning to run surface skimmer on the lily pipe out flow

Well 3/8" around the perimeter of your UNS 90U is equal to 26 square inches of room air intake area, 48 square inches with the lily pipe cut-out.

That sounds like a lot.. but your CO2 will be collecting under a total of 722 square inches of lid. That's about 7% opening for room air circulation

If the skimmer is under the open area, then it will be drawing in water at the point it is exposed to room air. That may help a bit.

I can say I had a very similar lid, with similar borders and corner cut-out, on a much smaller 45C. That setup did not adequately vent, although my skimmer was not placed in the opening, rather at the far side of the tank where it simply circulated the CO2 saturated surface water

This resulted in the loss of a number of invertebrates. Snails and shrimp are necessarily more fragile than fish are, so it partly depends on what your livestock will be.

I think across the hobby it's relatively uncommon to both inject quite high levels of CO2 to maximize plant growth, use a canister rather than a hang-on-back, and simultaneously fit a tight lid rather than either an open top, a screen top, a standard hinged top with the open strip area, or an open sump across the back

I'm interested to hear from other members with covered tanks and canister filters. My own experiences have been very frustrating, so I have ordered a new acrylic lid for this tank with perforations drilled for gas exchange.