Dispelling the myths about glass lids on reef aquariums.

[Peter Houde]

They prevent fish from jumping
-Some sort of jumping protection is a positive, a mesh top provides the same benefit.

They limit evaporation reducing your need for topoff water- expanding the duration your ato reservoir lasts.
-I'm a Kalkwasser user. More evaporation is a good thing, helps maintain better calc/alk/pH levels. My ATO and Kalk reactor reservoirs are hard plumbed, haven't manually filled a reservoir in years.

They limit humidity being added to your household air
-A wash... half the year, this is a positive, half the year, a negative. Again, evaporation is a good thing.

They limit evaporative heat loss allowing you to use much smaller heaters(risk mitigation) and save a significant amount of electricity($$$)
-A properly designed heating system, say an independent heater controller plugged into an Apex, is much better for risk mitigation than an undersized heater. A properly sized heater, running over less time, is more efficient than running an under sized one longer... and again, evaporation is good

They protect your expensive lights from rogue fish splashing
-Never had a splash problem with my lights, but I do run my lights a bit higher than many, at 14" or so over water level

Most importantly- they limit the effect that high CO2 household air has on your pH. Reducing gas exchange reduces carbonic acid addition to your reef.
-Gas exchange is a huge positive, in my opinion. Co2 is _released_ from the aquarium via gas exchange with the atmosphere, being a normal product of photosynthesis. If your pH is low, Kalkwasser, which requires high rates of evaporation for efficient use, boosts pH very effectively.

I'll stick with my mesh top, thanks.

COv2 is not produced by photosynthesis, O^2 is.

 

[kenchilada]

Glass tops suck and are gross. Fight me.

 

[Peter Houde]

I'm sorry-- I know these are different, but I don't understand what the difference is. I get that they have different chemical makeup, but I don't know when to use one versus the other. Would you please explain?

Off hand, I don't know about transmittance. I think the best thing to do is consult the manufacturer. As someone else said, some are specifically made to cut UV, others not.

 

[Mike konesky]

COv2 is not produced by photosynthesis, O^2 is.

True, but it is produced during respiration, which happens at night.

 

[Reefinmike]

You have no skimmer AND a closed top, and are not concerned about low O2 at night?

Ever measure it?

Never measured it but my fish have been fine for years. I’m not saying that O2 is perfect and ideal but i’m not seeing anything that shows it’s sub par and unhealthy.

 

[robby2782]

I started using glass tops again, and my acropora wasn't affected negatively at all. I saw less of an impact with my par meter when comparing, the difference, but the only con I found was I ended up putting a chiller on my aquarium to keep the temp at 77 degrees.

 

[Reefinmike]

I put it to you that your dirty glass wasn't that dirty blocking only an additional 2% of light lol. But in all seriousness I'm sure with salt creep and the water droplets/condensation it's more than that. I had glass lids but got rid of them, too much cleaning and to much of a greenhouse effect for my liking. Yes they keep fish from jumping but not many other reasons for it over something like a jump guard imo. You made some good points though. I also wouldn't say they are myths needed to be dispelled

This is just a simple, real world anecdotal test. I included pictures of the level of dirtyness accumulated over 6 weeks and noted that humidity water droplets were left in place for the dirty reading. Sure, I’ve seen much dirtier glass. Use a hot light like t5 or MH, keep a high water level, add a HOB skimmer spilling microbubbles into the reef and have 1” waves on your surface… you’ll get tons of salt creep in a week. Par will certainly drop more than 2%. I find it’s not difficult to keep glass clean for a month + if you avoid these scenarios.

I guess the basic point I’m trying to get across is that glass lids deserve another look. I feel their negative aspects far outweigh their benefits . Drives me crazy when some people say things like “glass lids are for freshwater tanks, reefs need to breathe. Glass lid bad”. My reef didn’t get the memo lol

 

[vetteguy53081]

Ive used glass since 1991 and always will.

 

[doubleshot00]

Idk about larger tanks but on a nano they heat up the tank. Ever since taking off my Fluval lid my tank doesn’t have over heating issues anymore.

 

[Chrisv.]

Idk about larger tanks but on a nano they heat up the tank. Ever since taking off my Fluval lid my tank doesn’t have over heating issues anymore.

This is a huge issue for me too. My nanos look like patients in the ICU with all kinds of cords and tubes coming out of the back chambers of the AIO. Lots of heat produced. Luckily my apex turns on a small fan.

 

[doubleshot00]

This is a huge issue for me too. My nanos look like patients in the ICU with all kinds of cords and tubes coming out of the back chambers of the AIO. Lots of heat produced. Luckily BB apex turns on a small fan.

Exactly. My wifes fluval is not appealing. Its in her office so she is the only one that sees it so.

 

[Chrisv.]

Exactly. My wifes fluval is not appealing. Its in her office so she is the only one that sees it so.

It's an excuse for me to blast the ac all summer. My wife hated it when I ran a chiller, and I like it when the house is cooler. Win win.

 

[JCTReefer]

Effects of various aquarium covers on light transmission

I got a private message from GaryE and thought my reply might be of interest to others. Here’s the message: I know you have done innumerable studies on the various different lighting packages available. Have you ever studied the effects of different coverings on PAR levels? Specifically, I'm...

www.reef2reef.com

 

[Suesea]

Totally, it's the first thing I do in the morning.

Nothing like the smell of a two stroke motor and a reef tank in the morning to get my juices flowing

 

[Mrsirtang]

I use corrugated clear polycarbonate roof panels.
>Most hardware stores carry them, fairly cheap
>They are 93% light transmission
>Light weight
>Easy to cut
>Durable
>They don't sag

​

 

[trainbob]

I have a perfecto glass lid but did not put the plastic strips on the back because didn’t like them. So far no fish has jumped out. Also is O2 oxygen a is there a simple and cheap way to test for it

 

[sdemon367]

People in the hobby often repeat what they hear others say-
- “Glass lids Are bad. They get dirty and block a lot of light”
- “Clean glass drops PAR 10-20%. On top of that, the dirt, salt creep and humidity drops cut par an another 10-15% so you have to increase your lights every week to account for this then back to baseline when tops are cleaned”



I’ve been using glass lids for 17 years and strongly feel their benefits far outweigh the par loss most modern lighting is able to overcome.

• They prevent fish from jumping
• They limit evaporation reducing your need for topoff water- expanding the duration your ato reservoir lasts.
• They limit humidity being added to your household air
• They limit evaporative heat loss allowing you to use much smaller heaters(risk mitigation) and save a significant amount of electricity($$$)
• They protect your expensive lights from rogue fish splashing
• Most importantly- they limit the effect that high CO2 household air has on your pH. Reducing gas exchange reduces carbonic acid addition to your reef.

I did a little 1 hour real world experiment using 3 new Neptune sky lights mounted over a 72”x18”x27” 150 gallon reef with admittedly yellow foggy water(I don’t use any filtration whatsoever). The bottom of the light is 3.0” above the glass, 5.0” above the water surface and 16.5” above the par sensor(11.5” under water). The par is measured with the neptune PMK(apogee sensor). The glass is a mix of what fits. Measurements were taken under the center 3.9mm thick piece of very scratched up tempered green glass. My current lighting is set to Neptune’s custom “sky” color recipe at 66% intensity. Readings were viewed without lag using the display module. All pumps were left running as usual and the average was taken after 5 minutes. My wav pumps are on 5 second alternating pulse so flow anomalies weren’t a factor.



SKY 66% - PAR - % of Max

Dirty glass - 227 - 89.0%

Clean glass - 232 - 91.0%

No glass - 255 - 100%



Sky 100%. - PAR - % of MAX

Clean glass - 330 - 89.2%

No glass - 370 - 100%



All ch 100% - PAR - % of MAX

Clean glass - 368 - 89.8%

No glass - 410 - 100%



In conclusion, clean glass cuts PAR by 10%(on average) vs no lid at all. Dirt buildup reduces PAR an additional 2%. Using my 66% sky setting as an example- if I wanted to emulate the par with no lid I just have to bump up intensity 7% to 73%. Glass lids work.

I believe this squashes the misconceptions surrounding PAR reduction however it does not address the potential shift in color spectrum. I’ll leave that up to someone who really wants to nit pick lass works for me. In another, much more thorough experiment I will address the pH “boosting”, topoff reducing and electric(heat) saving benefits of glass lids.





Image description

1- shows the amount of dirt allowed to accumulate on lids over 6 weeks

2- shows the general hazyness to the water. And wild coral growth provided glass lids don’t hold you back

3- par sensor location

4- shows the basicness of the setup. Random glass lids, hastily made light rack resting on two stacks of buckets- real world testing.

5- This is the center glass that readings were taken under. This is it CLEAN. Very hazy, scratched, hard water deposits

Great read. I've always wondered about this. I have a 140 with glass tops I had cut at a local glass shop for exact fit from front to back. Used 2inch hole hole saw in opposite corners for my return lines. I have three 250w halide and 4 96w PC bulbs. The light fixture is about like your setup with regards to height. Have had no issues growing any type of coral. I have had issues locating replacement 96w PC square pin bulbs. Replaced two in the front with some actinic led 95w strip I put in place of the 96pc.

 

[Suesea]

This is just a simple, real world anecdotal test. I included pictures of the level of dirtyness accumulated over 6 weeks and noted that humidity water droplets were left in place for the dirty reading. Sure, I’ve seen much dirtier glass. Use a hot light like t5 or MH, keep a high water level, add a HOB skimmer spilling microbubbles into the reef and have 1” waves on your surface… you’ll get tons of salt creep in a week. Par will certainly drop more than 2%. I find it’s not difficult to keep glass clean for a month + if you avoid these scenarios.

I guess the basic point I’m trying to get across is that glass lids deserve another look. I feel their negative aspects far outweigh their benefits . Drives me crazy when some people say things like “glass lids are for freshwater tanks, reefs need to breathe. Glass lid bad”. My reef didn’t get the memo lol

But in your last paragraph you said "I feel their negative aspects far outweigh their benefits" so...this means you use glass lids even though there are mostly negative aspects?

 

[Lavey29]

Nothing like the smell of a two stroke motor and a reef tank in the morning to get my juices flowing

And then blow the diesel carbon build up out of the pipes.

 

[sdemon367]

Very interesting. I never would’ve thought polycarbonate could have that much of an effect.

Some window glasses have light filtering films to limit UV and heat energy entering a building. I wouldn’t be surprised if some plastics intended for windows have similar properties.

If you have a local glass company they probably have glass you can have cut that has no filtering properties.