Need help with diy LED project

Hello, I am wanting to light my fishtank by using LED's... it is a really big fish tank so this must be a custom job, and i am interested in this field of work. I understand the basics of DC current, and i can solder... but i am still a n00b!

I have 100 LEDs just like these http://cgi.ebay.com/100-5mm-6000mcd-LED-Lamp-Ultra-Bright-Blue-LEDs-DIY_W0QQitemZ350034574270QQihZ022QQcategoryZ66948QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
and i was wanting to use like, 50 or more if you guys think i need it. I understand the need for resistors and my goal, if possible, is to use as few resistors as possible! since they are not readily available to me.

My plan is to use two long separate strands with, say 25 LEDS on each. Is this possible if i can find a 12v+?

is this possible?
Do i need to use series or parallel wiring? ( i want to use fewer resisters)
Can i make two separate strands using one power supply
Which values do i need to use to find resistors?

Thank you guys so much, I have been wanting to work on this project for a long time, but these questions have always kept me.

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tech-king9 years ago
i just found this thread, sorry to weigh in late. because this project is for a fishtank, the plug you use MUST BE A GFCI. otherwise, there is a risk of electrical shorts and fires. you can buy gfci outlets at any hardware store.
Interesting; I've had several (smallish) fishtanks over the years, and never seen the "requirement" for GFCI outlets. I mean, it sounds like a good idea, but "Must" ?? (I can see the importance going up as you add homebrew electronics...)
with homebrew electronics, yes. with store bought ones for underwater use, i would add one, but it would not be needed.
guyfrom7up9 years ago
well, a dirt cheap option, but not safe is to put all of them in series, put a specified resistor in sereis, a 1,4004 diode in series facing the opposite direction, and plug direclty into a wall. Not safe though cause you can be easily electricuted.

You could ge the 25.2 volt transformer from radioshack.
25.2/3.5=7.2 or 7 diodes in series with 1 resisotr
to have 49 leds you would need 7 resistors.
Lets see how many amps you need. 20mA per led (don't use 30, that's the MAX), so 0.02 times 49 = .98 amps, or pretty much 1 amps. The one at radioshack gives out 2 amps, so it should be fine
no offense, but that just screams out accident. at least put an isolation transformer.
I said you could do it, but it'd be very unsafe.
for future record, you should suggest a gfci outlet for all devices that plug into a wall and are near water. and yeah, you did say it was unsafe.
ground fault interupter?
Grond Fault Circuit Interrupter. it detects a ground fault condition and cuts power in milliseconds to prevent the high amperage short from forming. they are used as pluggs in kitchens and bathrooms
BZZZT! If you have 7 series circuits in parallel, with 7 LEDs in each series circuit, you will only need 140mA current total. You would only need the 1A if you put all 49 LEDs in parallel. ;-)
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