Confused/ Annoyed By Lighting

[TheChards]

Hi guys,

I’m confused, and a little frustrated by my lack of knowledge about lighting for my 33 US gallon fish tank. I’ve tried to read as much as I can find about lighting in general and have decided that, in order to be able to grow plants in this tank successfully, I will need at least 80w of lighting to achieve more than 2w per gallon (if this makes sense). However, the fittings in the hood will only allow for two 24” tubes (currently 20w each) and I am really struggling to find anything above 20w that’s 24” long. The only way I can see to be able to have higher output tubes is to have a longer fish tank but then surely this would contain a greater volume of water and the higher wattage tubes would then be inadequate.

How can I actually achieve this level of lighting? Do I need to replace the hood and find one which can house 4 tubes? Am I missing something?

This all seems very complicated and I feel like I’m the only person in the world who just doesn’t understand this!

Thanks,
Dan

 

[Colin_T]

Unfortunately most aquarium packages (tank, hood, etc) aren't designed for plants or corals. They are simple set ups designed for a few fish. Most hoods don't have room for more lights.
It is sometimes easier and cheaper to remove the hood and replace with a conventional aquarium light unit, (ie: Hi Output T5). The other option is to go for a metal halide light unit and hang it above the tank, but you will have to remove the hood for that too.

How big is the tank, dimensions (length x width x height)?
More light is required for taller tanks. Tanks that are 2ft or more high do best with metal halide light units. Tanks around 12-18inches high are usually fine with fluorescent globes.

 

[TheChards]

Hi Colin, thanks for your reply.

The tank in question is 80cm long, by 35cm wide, by 45cm deep. So I guess I'm right on the limit for fluorescent lighting. I'm surprised and a little frustrated at the amount of different tubes available considering that I can't find anything above 20w that would fit in this hood. Even if I replaced this hood, where would I find the fluorescent tubes to go in it?

 

[Colin_T]

2ft light units are generally only available in 18 or 20watt globes. Hi Output (HO) T5 fluorescent globes will give more light (wattage) per globe compared to normal fluoros (T8 globes).

You can get HO T5s from most petshops, hardware stores or lighting stores. They often sell them as slimline fluoros because the globes and units are thinner.

45cm high tanks are fine with fluoros, either normal (T8) or T5 globes.

The problem with a tank that is 80cm long is it is too short for a 3ft light unit, and too big for a 2ft light unit. You could get a 3ft light unit and have it hanging over the edges. You would have to remove the hood, or cut the sides out for the light unit to fit.
3ft fluoro globes come in higher wattages than 2ft globes.

 

[TheChards]

45cm high tanks are fine with fluoros, either normal (T8) or T5 globes.

Is there any reason why a 45cm high tank wouldn't be fine with normal t8s provided that the 2w per US gallon rule was met? Considering that the highest wattage I can find for a 24" t8 globe is 20w, the most light I can provide is 40w using t8s so I guess this won't be OK.

I shall have a look around and see whether t5s will be any better. Presumably I will need to replace the hood if I use t5s as they'll require a different fitting?

Thanks!
Dan

 

[Colin_T]

Normal T8 fluoros are fine on your tank. The main drawback being the length of the globe that is limiting you to the wattage. But having 2wpg is still fine for many plants. You will probably be a bit under that but again many plants will do ok. And you won't have to use CO2 with the lower light output.
You can also have the lights on for 16hours per day and that can provide more light for the plants, although it won't be any brighter for them, it will provide them with a longer period to photosynthesise and to grow.

If you get T5 globes you will need a T5 housing. HO T5s need a HO unit. The HO units have a different ballast in them and allows the HO globes to work.
You can usually swap the light units over in most hoods but it depends on the particular hood.

 

[TheChards]

So basically, unless I can settle with two 20w t8s providing me with 1.2w/ gallon then I will need to upgrade to HO (High Output?) t5s which will mean an HO unit and different ballasts as well as the t5 globes themselves. Is this correct?

What is the maximum output that t5s provide for a 24" globe? Do they go up to 35w? If so, two 35w globes would provide me with 70w in total and 2.1w/ gallon. If I went with this, I guess the real question would be whether or not I could fit the HO housing into the existing hood neatly.

Thanks for your patience and expert advice Colin, it is very much appreciated!

 

[aaronnorth]

2 x 20w HO T5's (1.2wpg) would be enough to grow most species of plants.

Are you going to be using CO2 injection & ferts for this tank?

 

[TheChards]

Is there any difference between 2 x 20w t8s compared to 2 x 20w t5s as they provide 1.2w per gallon?

I was planning on using CO2 injection and ferts but then the topic of lighting came up and I got confused. At the moment I'll just do whatever people tell me to...

 

[aaronnorth]

T5's have more watts per square inch, so they penetrate deeper, but they are also more powerful. If you get them you will notice a big difference. Generally, we double the answer to get an equivelent to T5's, so your levels with 2 x 20w T5's will be more like 2WPG anyway. If you seach some of supercoley1 tanks then he runs 0.9WPG T5 on a 30g tank, with plants such as blyxa japonica.
Providing enough nutrients & CO2 is just as important.

 

[Colin_T]

So basically, unless I can settle with two 20w t8s providing me with 1.2w/ gallon then I will need to upgrade to HO (High Output?)

yep

T5s which will mean an HO unit and different ballasts as well as the t5 globes themselves. Is this correct?

yep, you will need a new light unit if you get T5 globes. T5s are available in standard and hi output so if you get hi output globes, you will need a hi output light unit. If you get standard output T5s then you need a standard output T5 light unit.

What is the maximum output that t5s provide for a 24" globe? Do they go up to 35w?

Not sure but they usually do a higher wattage compared to normal T8 globes so you might find 35watt HO T5s if you look around. But as Aaron mentioned, a couple of 20w T5s will give you more light than a couple of 20w T8s.

If so, two 35w globes would provide me with 70w in total and 2.1w/ gallon. If I went with this, I guess the real question would be whether or not I could fit the HO housing into the existing hood neatly.

You should be able to get a T5 unit into a hood. They are the same length but a little narrower and not as high so they would take up a bit less space in the hood. But again it depends on the hood. Have a look inside the hood and see if the current light unit can be removed without too much trouble. If it can, then you should be able to replace it.

 

[SuperColey1]

I am guessing you have the same tank as me - a Fluval 125Ltr?

If so then check what the ballasts within the hood recess say on them. Mine came with 2 x 20W but the ballast was a 2 x 15W.

If yours is the same This means you haven't got 40W. You actually have 30W and it is underpowering the tubes

Basically 20W tubes are pointless unless you have a 20W ballast. If you have an 18W or 15W ballast then that is thepower the tubes will be running at.

As for growing conditions then with good quality CRI and decent K then you have enough light there for most plants. Forget about power and Lumens as they mean nothing in this hobby. You want spread meaning the light gets to all parts of the tank better

There is not a lot of difference between T5 and T8 wattage wise. For the same length they are about the same Watts. The difference is in HO where a T5HO will be much more wattage for the same length.

With mine (Aaron said I use them but I don't anymore as I made up a LED rig ) I managed to find some 29" T5HOs which were 30W each. I ended up using 1 of these on it's own as it was more than enough. Would take some searching for but I think Juwel use these too. You would of course need a T5 or T5HO ballast to go with the tubes.

AC

 

[TheChards]

Hi guys,

Many thanks for all the tips and suggestions. Considering the cost implications, I’ve decided to stick with the current 2 x 24” 20w t8s setup for the time being although I’m replacing the tubes (Sun-Glo for Power-Glo and Aqua-Glo for Flora-Glo – does this seem like a good combination?) and will see how things go. I’m also using root tabs, a daily fertiliser and a CO2 diffuser to try to maximise my chances. If everything goes horribly wrong then I will either cry and scrap my plans for a planted tank or look into upgrading the lighting unit to something that will take HO t5s and then cry.

SuperColey, the tank is a Fluval Due Deep 800 which some friends were getting rid of – hence the fact that I seem to know so little about it. I had no idea that the ballasts may be underpowered so thanks very much for giving me something else to look out for. It came new with 20w globes so I would have thought the ballasts should be 20w too but who knows!

Cheers everyone!

 

[*joanne*]

I had this problem with my tank only had 74w over 165l

In the end I changed to a interpet t5 compact unit and now have 110w over my tank.

 

[SuperColey1]

The tank in my sig is a Duo Deep 800!!!. The only original part I still use is....the tank

It has a 2 x 15W magnetic ballast in the ballast recess.

Therefore due to it being magnetic it is not as efficient as instant electronic ballasts which T5 use and nowhere near programmed electronic ballasts that T5HO use.

I did use 2 of the end caps from the original hood in a different setup but I connected them to an 18W programmed electronic ballast.

There was a very noticeable difference in brightness from the change from magnetic to programmed electronic and it doubt it was solely due to the 3W increase!!

Saying that with good tubes (the originals Sun and Aqua) are rubbish. The ones you bought seem to be a good choice. Do they look better?

AC