Perspex top

[ChrisP]

Hi all, I'm getting a bit tired of topping the tank up with water due to evaporation so I'd like to put a top on it. Does anyone know what thickness perspex is best to use to avoid it bending with the heat of the lighting? Also can anyone recommend an eBay seller for perspex / acrylic? I had a quick look on eBay and its more expensive than I thought

 

[tam]

Nope, but I'm watching this as I need to order some too. I've scrap pieces layered at the moment. So far... the 4mm with a lip (small strip glued to make a L shape) are fairly straight.

 

[HiNtZ]

Depending on tank size you may need to brace it to stop it sagging.

Very simple - cut the sheet to fit the tank then cut two 2" thick strips. One for left to right and another front to back (so like a cross).

Glue one strip standing up on its side to the underside then the other on its side on the top side.

The strips must be on their cut edge. Gluing the strip flat on the sheet will do nothing.

Think of the strips behavior like wood with a grain. The strip will bend and flex one way but not the other.

Hope that makes sense?

Having a strip on the top also helps with lifting it off the tank. Like a handle.

 

[mort]

If you have a dunelm or qd near you have a look at their clip picture frames (qd is better as they have larger sizes). I have just covered my signiture 600 with them for about £6 (with 2 45x30cm). They have really thin glass but are thick enough to not bend and I find they don't discolour as much over time. They are also easy to modify if you need to cut the corner off for lily pipes etc.

You can also pick up cheap lid holders that push onto the aquarium rim from eBay for a couple of quid should you need them.

 

[zozo]

Other point of interest, there are 2 types of Acrylic.. Casted Acrylic - GS and Extruded Acrylic - XT. The extruded acrylic production process leaves tension in the material.. It stays pretty straight if correctly supported and in a stable temperature invironment. But is it is warmed up it definitively starts to bend. Due to these internal tension it also cracks easier with cutting.

Casted Acrylic doesn't contain these tensions and there for much easier to cut etc.

But, it stays plastic and it's melting point is rather low. If not sufficiently supported and stressed by gravity it will already slightly lose form and bend at very low temperatures around 40°C. Even 10 mm GS acrylic sheet will very slowly bend if it is long term stressed by gravity at this temp if not suffieicently suported. Thus you would need to go with signficant more thickness than 10mm which makes it a tad too expensive creating a top aqaurium cover from it.

Than rather use glass and handle it with more care not to crack it. For example use little1mm thick rubber stickers on the corners and along the edges to prevent glass laying directly on glass.

 

[Nick Norman]

I Had 5mm Acrylic on my tank in two squares 400mm x 400mm. When it started to sag after a few weeks i turned them over until they sagged the other way. I glued tabs on each side so it located on the tank wall.

I currently have 3mm trays that i have made by gluing support around the edge that works quit well. It has sagged a bit as you can see in the photos.

 

[Matt @ ScapeEasy]

Just wondering about condensation... if a sheet of a flat material were placed on a open aquarium condensation would form on the sheet... just wondering though if at the edges there is a risk of it running down the outside of the aquarium due to surface tension etc and it wicking through the small to between the materials...?

 

[zozo]

Just wondering about condensation... if a sheet of a flat material were placed on a open aquarium condensation would form on the sheet... just wondering though if at the edges there is a risk of it running down the outside of the aquarium due to surface tension etc and it wicking through the small to between the materials...?

There are several types of supports available to hang to the glass edge. Than the cover will hang inside the tank about 10mm bellow the rim.
On ebay you find the acrylic or metal support hooks for aqaurium cover.

https://www.ebay.com/itm/Fish-Tank-...14d649a52:m:m7G7T9_KgGKR1p7_jd-dnyw:rk:8:pf:0

https://www.ebay.com/itm/6-8-10-12m...acb36db4b:m:mp7cEIScxb8paB73Vx2D8cQ:rk:1:pf:0

 

[X3NiTH]

You can get sheets of clear polycarbonate from B&Q 1.24m x 620mm x 4mm.

At 4mm thickness its a pig to cut (scoring and snapping can work but it's prone to breaking off line) but if you get it in store and you have your dimensions you need you can get them to cut it. Instead of a flat lid you can construct a box so you can have an air gap for emergent growth. It's easy to glue, I used Dichloromethane (Plastic Weld).

I used a wet diamond wheel tile cutter thingymabob to do the box construction on the 12L tank, and for the tank above I used a Dremmel Tool with various bits to do the job (cutting discs bound up and reamers made rough cuts and lots of mess, wasn't fun but got the job done).