I need a concise, ORIGINAL 3-4 paragraph definition / description for each of
the following four terms, as they relate to different types of fish tanks:

reef tank
saltwater tank (fish only)
planted tank
freshwater tank (fish only)

Not sure if you're still looking for info here, but here's my definition:

Reef Tank:  Has a slightly higher PH than a FO (Fish Only) Saltwater
tank. (around 8.3 - 8.4 in the daytime) I generally keep my reef tanks
slightly higher in temperature than FO, This speeds up growth, but be
careful as higher metabolism of the inhabitants mean problems could
spiral out of control much more quickly than lower temps.  Reef tanks
usually are meant to resemble a natural reef.  Live sand and rock are
often added to facilitate nitrate reduction into N2 and O2. 
Invertebrates are often included in reef tanks as natural scavengers
and sand sifters.  Corals (soft or hard) are prominent in reef tanks. 
Many times a reef tank is set up to house corals and fish function as
maintenance.  Filtration is important in reef tanks because you want
some live plankton to remain in your water so the corals can filter it
out and eat.  Generally needs more additives to keep inverts and coral
healthy.  (iodine, mobyleium, calcium, etc)

Saltwater Tank FO:  Sometimes called a FOLR (Fish Only With Live Rock)
if you have live rock in the tank.  Has a slightly lower PH than a
reef tank.  (about 8.2 - 8.3)  Usually does not have inverts or
corals.  Houses more agressive fish (Coral eating, invert eating
etc...)  Your substrate can be pretty much anything.  Reef tanks
should have crushed coral or other similar calcium carbonate (CaCO3)
substrate to help with buffering, but in FO tanks it's not necessary. 
Also corals need CaCO3 to build their skeleton. Additives are still
necessary, but not as important because of the lack of invert life.)

Planted tanks usually have a mub or similar substrate (for plant
nutrients).  Fish waste produces Nitrate which is converted by the
plants into N2 and O2.  Bacteria in non-planted tanks convert from NH3
to NO2 and NO3, but the NO3 cannot be removed from a fresh water tank
unless it's planted, or you do frequent water changes.  (10% 2x a
month)   Planted tanks need fish for the plants to thrive.

Freshwater FO tanks I've found are good for the more agressive
freshwater fish.   Cichlids tend to uproot live plants.  Because NO3
is not converted into O2 and N2 in a freshwater FO tank, you need to
perform regular water changes to prevent buildup of NO3.

Hope this helps.   Let me know if you have any more questions.

Hi there,

Thanks for answer - it's helpful, but not exactly what I was looking
for. I was hoping for a definition that would cater to more of a
newbie (and slightly less technical in nature). For example, the
defitions should be more explicity (early on) as to what animals and
setup is included in each type of tank (and also what's not included).
Also, freshwater FO tanks are also most common for beginners correct,
and don't necessarily need to house aggressive fish? Perhaps also some
sentences on why aquarists choose one type of tank vs. another. Can
you revise your definitions some? You seem quite knowledgeable on the
topic. Thank you!