This is my little brother's fire/water deck, he wishes to have the deck improved on.

Creatures:

4x Marine Flower
2x Hunter Fish
2x Phantom Fish
2x Revolver Fish
2x Aqua Knight
2x Aqua Hulcus
2x Crystal Lancer
4x Deadly Fighter Braid Claw
2x Immortal Baron Vorg
4x Mini Titan Gett
2x Bolshack Dragon
2x Metal Wing Skyterror

Spells:

4x Brain Serum
4x Tornado Flame
2x Rumble Gate

He wants this deck improved on because he is really struggling to beat my enlightenment deck, he has only beaten it once (he is the only person who has beaten it mind you). Please rate and fix it.

I run fire/water, but mine looks like this
fire
4 tornado flame
4 Validos
4 rothus
4 vorg
4 zyler
4 crimmson hammer
4 braid claw

water
4 brain serum
4 aqua hulcas
4 spiral gate

This deck has never lost.

Sage of Fire's deck is good but i think if you want to use Fire/Water or any 2 color deck i think the civs should be more evened out to get the full impact of each in the deck. Your Brother could use this if or when he gets the cards:

--Creatures--
4 Deadly Fighter Braid Claw
4 Immortal Baron, Vorg
4 Mini Titan Gett/Brawler Zyler
4 Aqua Hulcus
2 Corile
2 Rothus, the Traveler
2 Armored Blaster Valdios
2 Crystal Lancer

--Spells--
4 Brain Serum
4 Spiral Gate
4 Crimson Hammer
4 Tornado Flame

Hope this helps

I agree with CrimsonBrawler.
Depending on your meta consider changing the quantity of the following cards:
Corille
Rothus
Valdios

Also fool around with Teleportation, Engineer Kipo and Magma Gazer. If you cannot find the Valdios replace then with Magma Gazer.

Ah, thanks Brawler for showing him the deck I've been using for a while now even if you didn't know it. Both CrimsonBrawler and gabbahh present good points; the deck's colors are quite compatible with each other and the best thing you can do is experiment with different cards (i.e. the ones gabbahh mentioned) since that can make the difference between easy and difficult battles. That reminds me, I need to start working on my deck again to see if I can improve it. That's my two cents.

Another deck for you to see:

4x Aqua Hulcus
2x Corile

4x Spiral Gate
4x Brain Serum
2x Teleportation

4x Mini Titan Gett
4x Brawler Zyler
4x Rothus, the Travler
4x Armored Blaster Valdios

4x Crimson Hammer
4x Tornado Flame

I like some of these mods, however my little brother doesn't. He likes having blockers in the deck. He believes that without them he will be dead before you could say duelmasters. Any further mods on the deck with blockers would be great or should he switch to light/fire?

I have been playing red blue also. Tested an ok red/blue build again an ok rush build. You do not need the blockers, since you have enough burn and bounce. Blockers are just cards sitting there and doing nothing... until you decide to sacrifice them. Also even if you want to use blockers 12 is a bit much... Especially since your not playing diamond cutter.

If you want Blockers try this:

4x Marine Flower
4x Hunter Fish
4x Aqua Hulcus

4x Spiral Gate
4x Brain Serum

4x Brawler Zyler
4x Mini Titan Gett
4x Rothus, the Traveler
4x Armored Blaster Valdios

4x Tornado Flame

Er.. I'm the little brother speaking. I like all of the decks, but I prefer Crimson Brawlers' deck except i have changed a little bit.
Valdios -2
Bolshack Dragon +2
So, thanx to everyone!