Ira

No.  I don't know of any good locally available RO/DI, but there are many off Aliexpress and similar.  Someone else will have to point you towards one.

Cees...Hmmm...That name sounds vaguely familiar....:)

You also should probably have a small powerhead or two in the main tank for circulation in addition to the return pump.

Waxeye - Zosterops lateralis
 
 

 
 

Have you tried telling it to mind its own business?

Odd, the link to the ones I bought above redirects back to this thread.   https://www.amazon.com/gp/product/B00D83BGVS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1   Try copy and pasting. 
Part of the problem is you can't really trust you're going to get the exact same thing each time, or the quality.  Like, I bought two orders of 3 rolls.  The second order was different.  BUT!  They're cheap enough it's not really a disaster if they're not exactly matched.  Try aliexpress or bang good for SMD 5630s, might be cheaper than Amazon
 
 

Yeah,  my tank is probably in the region of 20 years old too.  Interesting to think my tank was probably built half my life ago. 
But...from the sounds of it, you're not really getting anything out of the tank.  If you're not enjoying it anymore, give it and the livestock up to someone who will.

Prefers a planted aquarium....Only because they like eating the plants.

Prefers a planted aquarium....Only because they like eating the plants.

Prefers a planted aquarium....Only because they like eating the plants.

Too artificial?  It doesn't get much less artificial than rain water. 
 
I use a very complicated process to deal with my rain water.
1. Connect hose to kitchen tap.
2. Put other end in tank.
3. Turn water on and adjust temp.
 
I do put a few handfuls of coral fingers and rock in my filters because it helps keep the PH from dropping.  But I haven't actually checked the PH in years.

Good to hear a shop refusing to sell fish if they don't think you can house them properly.
 
I think Wellington tap water is fine, but I've never used it.

Too artificial?  It doesn't get much less artificial than rain water. 
 
I use a very complicated process to deal with my rain water.
1. Connect hose to kitchen tap.
2. Put other end in tank.
3. Turn water on and adjust temp.
 
I do put a few handfuls of coral fingers and rock in my filters because it helps keep the PH from dropping.  But I haven't actually checked the PH in years.

Unfortunately, I found it dead this morning with a big chunk bitten out of it.  I'm not sure which fish killed it, but I'm thinking it was probably one of the severums.
 

 

My father in law bought me a fish for my Bday,  can anyone help ID it?
It doesn't move around a lot, and it's getting harassed a bit by the other fish.  I think it might be a female bristlenose?
 

Here's another pic, I think it's trying to dig around in the sand for food.

 
 

Unfortunately, I found it dead this morning with a big chunk bitten out of it.  I'm not sure which fish killed it, but I'm thinking it was probably one of the severums.
 

 

Good thing I don't expect to go on any trips in the next year or so.

Don't spill it on your hands, don't drink it.

I tried to make it a little bit entertaining.

So,  I bought some cheap LED strip lights and put them into my 4ft, 400L tank.
 
So, a bit of a build log:
 
 

Day 1, 0 hours.
Here's the tank hood,  was 6 24 watt CFLs(3 burned out) and two 4 foot fluoros(Dead)
 
 

Day 1, 1.5 hours
All the old lights pulled out, cleaned up, a bit of bleach and meths to clean up the wood.  And I've started cutting wires ready to solder to the LED strips
 

Day 1, 2.5 hours
Pre-tinning the wires and then pressing down onto the little copper pads seems to work...HORRIBLY, These things are horrible to solder,  little tiny pad and melty plastic all around it?!?  Ok, well, I managed to do it, kinda ugly...But ok.
 

Day 1, 3.5 hours
Slowly working through all the strips, one by one and throwing them in a pile....
 

Day 1, 4 hours
Laying them out in the hood, piling anything convenient on top of them to keep them from rolling up...
 

Day 1, 4 hours
I swear, I didn't do that....
 

Day 1, 5 hours
All laid out,  wires all joined together...
 

Day 1, 5 hours
Ugh...That looks horrible.  I'll figure out how to tidy it up tomorrow.
 
Day 2
I can't be bothered with it...
 
Day 3 
Oh, I know, I'll get some brass rods and solder the wires to it like bus bars.  It will look cool!  Should make expanding it easy too.
 
Day 4
Can't get to a place to buy the rods.
 
Day 5
Got them!
 

Day 6
AHHH, this looks even worse!  I didn't consider how much heat it would take to solder to giant rods, big, ugly cold solder joints EVERYWHERE.
 
And I ended up pulling off half the solder pads and wires from the LED strips.  I'm going to have to start this all over.
 

Day 7 Hour 1
Got some chocolate blocks/ screw terminals, should work a little better....
 

Day 7 Hour 2
Looking much more tidy now.
 

Day 7 Hour 4
I cut ends of the strips off, left the entire solder pad this time,  should only lose a little bit of light.
New wires soldered on, went MUCH better this time.  Same process, pre-tin the wires then press down on the solder pads.
 

Day 7 Hour 5
First set plugged in and powered up!  Oops, one strip isn't working... Just didn't get the wire into the terminal before screwing it down so it came loose.
 

Day 7 Hour 6
The rest of the strips are wired in and powered up,  I've adjusted the voltage on the power supply to 13v and it's drawing 90 watts.
 

Ok, 12.85 volts, the voltage dropped a little...
 
 

Day 7 Hour 7
All ready to go, I've put some liquid electrical tape where the wires are soldered to the strips, and on each of the solder pads the rest of the strips.  I've put on the sides too there, so hopefully it will hold the strips down, the adhesive backing isn't the greatest.
 
Oh, and there are a couple LEDs in the lower right that are dead.  I...Uhh....May have not noticed that strip fall on the floor at some point and then I may have stepped on it...
 

Day 8
Fish are happy to have some light, I think.

I turned the voltage back down to 12v, the lights are drawing 60 watts at this voltage.   They look brighter than the 3, year or so old 24w CFLs, but that's not hard.  It's a moderate brightness, I'd say, not really bright but good.  I'm pretty happy with them.  I think I'll buy more strips and add a bit more power.
 
 
The parts:
The LEDs
https://www.amazon.com/gp/product/B00D83BGVS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
 
Total about $25
 
The power supply, 150w 12v
https://www.amazon.com/gp/product/B00DECSE8G/ref=pe_2602560_239856390_em_1p_0_ti
 
Bought locally, $80
 
All the wires, screw terminals, solder etc you can find anywhere, I'm not going to link to those.  A wire stripper, liquid electrical tape, odds and ends another $50 NZ
 
Total cost: About $155
 
Maybe I should have spent a little more and bought a nice LED fixture....Oh well.
 

So,  I bought some cheap LED strip lights and put them into my 4ft, 400L tank.
 
So, a bit of a build log:
 
 

Day 1, 0 hours.
Here's the tank hood,  was 6 24 watt CFLs(3 burned out) and two 4 foot fluoros(Dead)
 
 

Day 1, 1.5 hours
All the old lights pulled out, cleaned up, a bit of bleach and meths to clean up the wood.  And I've started cutting wires ready to solder to the LED strips
 

Day 1, 2.5 hours
Pre-tinning the wires and then pressing down onto the little copper pads seems to work...HORRIBLY, These things are horrible to solder,  little tiny pad and melty plastic all around it?!?  Ok, well, I managed to do it, kinda ugly...But ok.
 

Day 1, 3.5 hours
Slowly working through all the strips, one by one and throwing them in a pile....
 

Day 1, 4 hours
Laying them out in the hood, piling anything convenient on top of them to keep them from rolling up...
 

Day 1, 4 hours
I swear, I didn't do that....
 

Day 1, 5 hours
All laid out,  wires all joined together...
 

Day 1, 5 hours
Ugh...That looks horrible.  I'll figure out how to tidy it up tomorrow.
 
Day 2
I can't be bothered with it...
 
Day 3 
Oh, I know, I'll get some brass rods and solder the wires to it like bus bars.  It will look cool!  Should make expanding it easy too.
 
Day 4
Can't get to a place to buy the rods.
 
Day 5
Got them!
 

Day 6
AHHH, this looks even worse!  I didn't consider how much heat it would take to solder to giant rods, big, ugly cold solder joints EVERYWHERE.
 
And I ended up pulling off half the solder pads and wires from the LED strips.  I'm going to have to start this all over.
 

Day 7 Hour 1
Got some chocolate blocks/ screw terminals, should work a little better....
 

Day 7 Hour 2
Looking much more tidy now.
 

Day 7 Hour 4
I cut ends of the strips off, left the entire solder pad this time,  should only lose a little bit of light.
New wires soldered on, went MUCH better this time.  Same process, pre-tin the wires then press down on the solder pads.
 

Day 7 Hour 5
First set plugged in and powered up!  Oops, one strip isn't working... Just didn't get the wire into the terminal before screwing it down so it came loose.
 

Day 7 Hour 6
The rest of the strips are wired in and powered up,  I've adjusted the voltage on the power supply to 13v and it's drawing 90 watts.
 

Ok, 12.85 volts, the voltage dropped a little...
 
 

Day 7 Hour 7
All ready to go, I've put some liquid electrical tape where the wires are soldered to the strips, and on each of the solder pads the rest of the strips.  I've put on the sides too there, so hopefully it will hold the strips down, the adhesive backing isn't the greatest.
 
Oh, and there are a couple LEDs in the lower right that are dead.  I...Uhh....May have not noticed that strip fall on the floor at some point and then I may have stepped on it...
 

Day 8
Fish are happy to have some light, I think.

I turned the voltage back down to 12v, the lights are drawing 60 watts at this voltage.   They look brighter than the 3, year or so old 24w CFLs, but that's not hard.  It's a moderate brightness, I'd say, not really bright but good.  I'm pretty happy with them.  I think I'll buy more strips and add a bit more power.
 
 
The parts:
The LEDs
https://www.amazon.com/gp/product/B00D83BGVS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
 
Total about $25
 
The power supply, 150w 12v
https://www.amazon.com/gp/product/B00DECSE8G/ref=pe_2602560_239856390_em_1p_0_ti
 
Bought locally, $80
 
All the wires, screw terminals, solder etc you can find anywhere, I'm not going to link to those.  A wire stripper, liquid electrical tape, odds and ends another $50 NZ
 
Total cost: About $155
 
Maybe I should have spent a little more and bought a nice LED fixture....Oh well.
 

1.  Yes.  The standard half dozen or so.
2.  They're basically non aggressive, so any other moderately sized active fish. 
3.  I'd say something in the 4 foot, 400L range minimum.  More mature you're looking at 6-8 foot.
 

1.  Yes.  The standard half dozen or so.
2.  They're basically non aggressive, so any other moderately sized active fish. 
3.  I'd say something in the 4 foot, 400L range minimum.  More mature you're looking at 6-8 foot.
 

Is there a reason you want to use plywood rather than glass?  That small size glass is going to be pretty inexpensive anyway.  And the whole tanks go for pretty cheap.
Cheapest lighting would be something like a 4 foot fluoro fitting, or even a couple small clip on lamps.  Which 10w floodlights are you talking about?
Better to go with a good canister filter than a sponge filter.

Ah, those ones.  I got the impression from some other threads that those were pretty poor color rendering and not a good spectrum for plants.  But haven't looked too closely into it and there is a metric buttload of various ones.