Glass tops

ken55 · 03/02/2012, 06:24 AM

Hello again!

I noticed in other threads that having tops on the tank was frowned upon, as rapid evaporation was supposed to be a good thing. I had tops on mine and, took them off. Yup, my evaporation rate went way up. Topping off every couple of days now so I guess I'm doing it right.

I admit that I don't understand the reasoning behind this. Will somebody tell me why the evaporation is a good thing?

Peter T · 03/02/2012, 07:27 AM

Quote:

Originally Posted by ken55

Hello again!

I noticed in other threads that having tops on the tank was frowned upon, as rapid evaporation was supposed to be a good thing. I had tops on mine and, took them off. Yup, my evaporation rate went way up. Topping off every couple of days now so I guess I'm doing it right.

I admit that I don't understand the reasoning behind this. Will somebody tell me why the evaporation is a good thing?

Evaporation helps keep the temperature of the tank lower. This is especially important if you are running halides on your tank as halides generate quite a bit of heat.

Covered tops also allow more build up of CO2 in your system. Open tops help gas exchange so your water stays more oxygenated. Every system setup is different and some people have no issues with low oxygen in the water even with a closed top. It depends on so many other factors as well.

BigCountry74 · 03/02/2012, 07:34 AM

Most people remove their glass tops for lighting purposes. Glass reflects like 10+-% of the light coming in. If you run a sump, you get your O2 there. But if you do not like Peter said be careful with a sealed top.

ken55 · 03/02/2012, 08:23 AM

Thanks Guys,

The heat from halides doesn't apply to me but the gas exchange makes sense. I am running a hob skimmer. Do you think I get enough Oxygen from that?

The reason I ask is that I have two toddlers in the house and I cringe at the thought of them pouring milk (or who knows what) into the tank. They see me doing water changes and top-offs. You know how they want to "help", especialy when your not looking.

Felix T Cat · 03/02/2012, 08:28 AM

I run my tank open top except when I'm going to be traveling for a few days and then I put the tops on to minimize evap rates while I'm gone.

Peter T · 03/02/2012, 08:50 AM

Quote:

Originally Posted by ken55

Thanks Guys,

The heat from halides doesn't apply to me but the gas exchange makes sense. I am running a hob skimmer. Do you think I get enough Oxygen from that?

The reason I ask is that I have two toddlers in the house and I cringe at the thought of them pouring milk (or who knows what) into the tank. They see me doing water changes and top-offs. You know how they want to "help", especialy when your not looking.

Hmm, I'm not sure as I don't have experience with HOB skimmers. But, the best way to test this is. Uncover the tank for a day or two and observe your fish. Cover the tank up again and see if they behave differently. If they appear more sluggish, breathe harder, or seemed more distressed, you have your answer.

ken55 · 03/02/2012, 09:00 AM

Quote:

Originally Posted by Peter T

Hmm, I'm not sure as I don't have experience with HOB skimmers. But, the best way to test this is. Uncover the tank for a day or two and observe your fish. Cover the tank up again and see if they behave differently. If they appear more sluggish, breathe harder, or seemed more distressed, you have your answer.

Thank you very much.

kzooreefer · 03/02/2012, 09:00 AM

I have had a glass top on my sumpless system for 6 years with no problems, its open a couple of inches in the back to allow for the HOB skimmer intake and output tubes. The skimmer itself provides more than enough gas exchange for the system.

ken55 · 03/02/2012, 09:06 AM

Quote:

Originally Posted by kzooreefer

I have had a glass top on my sumpless system for 6 years with no problems, its open a couple of inches in the back to allow for the HOB skimmer intake and output tubes. The skimmer itself provides more than enough gas exchange for the system.

Mine also has that 3 +/- inch gap at the back when the top is installed.
Thank you very much.

uncleof6 · 03/02/2012, 04:00 PM

Quote:

Originally Posted by BigCountry74

Most people remove their glass tops for lighting purposes. Glass reflects like 10+-% of the light coming in. If you run a sump, you get your O2 there. But if you do not like Peter said be careful with a sealed top.

This is not exactly accurate. Gas exchange is a question of surface area to volume ratio. The sump simply does not have enough surface area to compensate for the DT.

uncleof6 · 03/02/2012, 04:20 PM

Quote:

Originally Posted by kzooreefer

I have had a glass top on my sumpless system for 6 years with no problems, its open a couple of inches in the back to allow for the HOB skimmer intake and output tubes. The skimmer itself provides more than enough gas exchange for the system.

This is not entirely accurate either, and is not demonstrable. In practice, the same system, without a skimmer has x amount of oxygen, and the system with a skimmer has x amount of oxygen. The difference is not significant enough to claim the skimmer accomplishes this.

The movement of CO2 on the other hand, due to its higher solubility in water, is demonstrable, with the difference between "in room air" as opposed to "outside fresh air," however does not show an increase in dissolved oxygen--directly related to the skimmer--direct observation over a considerable time. Most of this process (O2 movement) would occur only in the pump volute itself, in the case of a needle wheel, or in the towers of a down draft, or beckett type skimmer, similar to an O2 reactor. But again, this has not been shown to be significant, by any controlled investigation. Such increases, could likely be depleted within the skimmer body, due to bacterial activity around the concentrated collecting of organics, and subsequent byproducts. The bubbles themselves, will account for no exchange (surface tension.)

Toddrtrex · 03/02/2012, 04:56 PM

Quote:

Originally Posted by uncleof6

This is not exactly accurate. Gas exchange is a question of surface area to volume ratio. The sump simply does not have enough surface area to compensate for the DT.

How can you state that without knowing the size of the sump? Also, you don't know if there is a skimmer in the sump.

uncleof6 · 03/02/2012, 04:59 PM

Quote:

Originally Posted by Toddrtrex

How can you state that without knowing the size of the sump? Also, you don't know if there is a skimmer in the sump.

Common sense. The skimmer contributes little to the process.

Toddrtrex · 03/02/2012, 05:00 PM

So, you are stating a fact without all the information?

Yes, skimmer do contribute.

ken55 · 03/02/2012, 05:28 PM

I seem to have kicked the nest again.

I have no degree other than a H.S. Diploma, but it seems to me that air goes in, makes bubbles, and "bubbled water" comes out the other side. There has to be at least SOME oxygen in it. How much? I'm not qualified to say.

sporto0 · 03/02/2012, 06:02 PM

Glass tops have been used for as long as I have owned a fish tank, somewhere around 1967, so this newer trend toward screen tops has much more to do with light refraction & heat than it does with gas exchange, sure there is a little more exchange without a solid lid, but they wouldn't even be available if there was issue with it harming your fish or your water parameters, oxygen does not need much of a gap to get in, it's all around us all the time. I would use the tops until my kids were old enough to understand why not to throw things in the tank. Sometimes these things can be overthought.

ken55 · 03/02/2012, 06:29 PM

Quote:

Originally Posted by sporto0

Glass tops have been used for as long as I have owned a fish tank, somewhere around 1967, so this newer trend toward screen tops has much more to do with light refraction & heat than it does with gas exchange, sure there is a little more exchange without a solid lid, but they wouldn't even be available if there was issue with it harming your fish or your water parameters, oxygen does not need much of a gap to get in, it's all around us all the time. I would use the tops until my kids were old enough to understand why not to throw things in the tank. Sometimes these things can be overthought.

Thank you for bringing this back to my original questions. As a newbie I am awash in a sea (pun alert) of information. I don't always know how to filter (again) through it.

bertoni · 03/05/2012, 08:42 PM

Depending on the situation, a glass top might reduce aeration to some extent. I've run tanks with and without tops, and the only difference I saw was the evaporation rate, but my tanks were lightly stocked with fish, if they had any fish at all, and I was careful about having a skimmer and good surface motion.

Yes, skimmers provide a lot of aeration by increasing the effective surface area for gas exchange. There's more in the chemistry forum on this topic.

rathos · 03/05/2012, 11:19 PM

Depending on your fish you might want a top, if all you have is a glass top then use it. I just lost a Gobi after having it for 12 hours because he jumped out of my tank. I fell for the "no glass top" advice. I switched to LEDs today to keep the temp down, but for the last few days I just turned down my heater and it seemed to hold the temp just fine. If you are not going to use a glass top get something, or at least don't buy any jumping fish. On a side note anyone know of a good place to get netting or a screen top that can accomodate HOB filters?

03/02/2012, 06:24 AM	#1
ken55 A wing and a prayer Join Date: Feb 2012 Location: SoChes Posts: 635	Glass tops Hello again! I noticed in other threads that having tops on the tank was frowned upon, as rapid evaporation was supposed to be a good thing. I had tops on mine and, took them off. Yup, my evaporation rate went way up. Topping off every couple of days now so I guess I'm doing it right. I admit that I don't understand the reasoning behind this. Will somebody tell me why the evaporation is a good thing?

03/02/2012, 07:34 AM	#3
BigCountry74 Registered Member Join Date: Feb 2012 Location: Charlotte, NC Posts: 1,761	Most people remove their glass tops for lighting purposes. Glass reflects like 10+-% of the light coming in. If you run a sump, you get your O2 there. But if you do not like Peter said be careful with a sealed top. __________________ 135g mixed reef (retired) http://www.reefcentral.com/forums/showthread.php?t=2132815 Current 40g reef http://www.reefcentral.com/forums/showthread.php?t=2483250 Current Tank Info: 40g bare bottom reef

03/02/2012, 09:00 AM	#8
kzooreefer Registered Member Join Date: Jan 2007 Location: Michigan Posts: 453	I have had a glass top on my sumpless system for 6 years with no problems, its open a couple of inches in the back to allow for the HOB skimmer intake and output tubes. The skimmer itself provides more than enough gas exchange for the system. __________________ Tank.........29-gallon glass Lighting.....Current Orbit Marine LED Filtration....Reef Octopus BH90 HOB Skimmer, GFO Reactor. Flow..........2 Jebao WP10 Powerheads

03/02/2012, 05:00 PM	#14
Toddrtrex Registered Member Join Date: Feb 2004 Location: Carol Stream, IL Posts: 23,162	So, you are stating a fact without all the information? Yes, skimmer do contribute. __________________ Click my name and then "visit toddrtrex's homepage" for tank pictures Current Tank Info: 210g reef and 65g reef

03/05/2012, 08:42 PM	#18
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	Depending on the situation, a glass top might reduce aeration to some extent. I've run tanks with and without tops, and the only difference I saw was the evaporation rate, but my tanks were lightly stocked with fish, if they had any fish at all, and I was careful about having a skimmer and good surface motion. Yes, skimmers provide a lot of aeration by increasing the effective surface area for gas exchange. There's more in the chemistry forum on this topic. __________________ Jonathan Bertoni

03/02/2012, 08:23 AM	#4
ken55 A wing and a prayer Join Date: Feb 2012 Location: SoChes Posts: 635	Thanks Guys, The heat from halides doesn't apply to me but the gas exchange makes sense. I am running a hob skimmer. Do you think I get enough Oxygen from that? The reason I ask is that I have two toddlers in the house and I cringe at the thought of them pouring milk (or who knows what) into the tank. They see me doing water changes and top-offs. You know how they want to "help", especialy when your not looking.

03/02/2012, 08:28 AM	#5
Felix T Cat Registered Member Join Date: Jan 2009 Location: Honey Brook, PA Posts: 557	I run my tank open top except when I'm going to be traveling for a few days and then I put the tops on to minimize evap rates while I'm gone.

03/02/2012, 05:28 PM	#15
ken55 A wing and a prayer Join Date: Feb 2012 Location: SoChes Posts: 635	I seem to have kicked the nest again. I have no degree other than a H.S. Diploma, but it seems to me that air goes in, makes bubbles, and "bubbled water" comes out the other side. There has to be at least SOME oxygen in it. How much? I'm not qualified to say.

03/02/2012, 06:02 PM	#16
sporto0 Moved On Join Date: Apr 2010 Location: Pittsburgh, Pa. Posts: 2,924	Glass tops have been used for as long as I have owned a fish tank, somewhere around 1967, so this newer trend toward screen tops has much more to do with light refraction & heat than it does with gas exchange, sure there is a little more exchange without a solid lid, but they wouldn't even be available if there was issue with it harming your fish or your water parameters, oxygen does not need much of a gap to get in, it's all around us all the time. I would use the tops until my kids were old enough to understand why not to throw things in the tank. Sometimes these things can be overthought.

03/05/2012, 11:19 PM	#19
rathos Registered Member Join Date: Feb 2012 Posts: 99	Depending on your fish you might want a top, if all you have is a glass top then use it. I just lost a Gobi after having it for 12 hours because he jumped out of my tank. I fell for the "no glass top" advice. I switched to LEDs today to keep the temp down, but for the last few days I just turned down my heater and it seemed to hold the temp just fine. If you are not going to use a glass top get something, or at least don't buy any jumping fish. On a side note anyone know of a good place to get netting or a screen top that can accomodate HOB filters?