In article , (Richard Sexton) wrote:

In article ,
John wrote:
Can anyone who's had experience building plywood aquariums recommend a good
2 part fiberglass resin or marine epoxy paint thats safe for aquarium use?
Home Depot and the boat marinas in my area don't have a clue.

No, they wouln't, but if youask the question "I have a wooden
boat I'm planning to store eyar round in salt water, what
whould I use to protect the wood" you'll get a better answer.

_The Living Aquarium_ (ISBN 0-517-39041-8) has instructions to
build all sorts of tanks out of all sorts of things; plywood,
glass-reinforced-resin, acrylic etc. For plywood they recommend
"varnish or resin". That's really all they say.

Everybody I know whose built a plywood tank (a handfull of
people I'd guess, over 30 years) used "marine expoxy".

Having said that I'm not convinced there's any reason to
build a plywood tank. You still have to buy the front glass;
decent plywood is not cheap (they recommend marine (mahogany)
ply which here is $80 a sheet) and large used tanks can be had
for peanuts if you're patient.

It doesn't make sense unless you build a really large tank, where really
large is ~200 gallons. However, as you'll read below, I believe that
cooling in these plywood hybrids may be a significant issue.

Plain old decent 3/4" plywood works fine. There's no reason at all to use
marine plywood. If your water is leaking past your sealing layers into
your wood, you're already screwed. Having fancy wood isn't going to
salvage the situation.

If you want a nice finish, it's usually cheaper to use something like A/B
or A/C plywood (A side to the inside), and then glue a finely finished
1/8" plywood onto the outside. Glue on an oversized piece and then trim
it with a router bit--the one that has a roller on the bottom and a
cutting blade flush with the roller just above the roller. Use one of the
wood adhesives that you paint on both surfaces, allow to dry to tackiness
and then bond on contact.

The above works better if you have a roommate who just took a cabinetry
class. :-)

The article I read in FAMA back in the late 70s recommended two coats of
fiberglass (for strength) followed by two coats of epoxy for chemical
stability. Apparently fiberglass can go brittle when exposed to water for
a long time. It may be overkill after all that fiberglass and epoxy, but
I also silicon all the inside corners.

I just used the fiberglass resin sold at hardware stores in 1 gallon cans
with a hardener in a separate little tube on top. For the epoxy, I don't
remember the brand but I got it from a local boat building/repairing
shop. The compounds were clear and they sold a variety of pigments that
could be added to the epoxy to achieve many colors. I used black which
may have been a mistake.

My tank is 6' long, 2' wide and 2.5' tall. That's about 30 cubic feet or
about 200 gallons (7.5 X 30 = 225, but that's outside dimensions).

My roommate at the time and I were both plant enthusiasts, so we built a
hood with ten 40 watt fluorescent bulbs in the middle four feet. At the
ends were two 75 watt spots per side.

After two weeks of operation (14/10 hour light cycle) the tank was about
10 degrees F above room temperature, or too hot to sustain the plants.

Now that may be too much light for that size tank, but from reading the
postings here, it doesn't seem like it. I see many recommendations of 3 -
4 watts of light per gallon of aquarium. I see very few complaints about
insolvable heat problems.

I suspect that a plywood tank cools significantly slower than an all glass
aquarium. Enough slower--or put another way, a glass aquarium is capable
of radiating waste heat at a surprisingly high rate--that a wood and glass
tank just can't take a good lighting system.

I'm not certain about the above and after seventeen years (yes, we built
this tank in 89), and nine years with no fish in the tank, I'm about ready
to do some testing.

I figure I'll start by taking a lot of temperature readings. Measure the
room temperature and the tank temperature while operating no lights in the
tank for a week. Then turn on two 40 watt bulbs on a twelve hour cycle
and take measurements for another week. Then four 40 watt bulbs. Etc.
That should tell me about how many watts the aquarium can radiate away
without supplemental cooling.

Lighting technology has changed a fair bit in the last decade.

I am a bit surprised by how many folks choose high output T5s or Power
Compacts. They let you squeeze more light intensity (more total watts)
into smaller areas, but they don't appear to be the most efficient in
terms of light intensity per watt consumed. As far as I can tell, the
linear T5 bulbs with normal output (non-HO) are the most efficient
lights. For example, the 28 Watt 48" (46.5") T5. For a given spectrum
(e.g. 3500K, 5000K, 6500K) the linear T5 seems to deliver more lumens than
T8s, or HO T5s (e.g. 54 watt, 48", or all the neat lights AHSupply sells).

In fact, in all categories, the dual tube compacts appear to be less
efficient than the linear tube T5s. They are nice at fitting into small
or odd spaces, but if you have a 48" or even a 36" long tank, I'm not sure
why you'd use the dual tube compacts, when the linear tubes are more
efficient.

Am I the only person in the hobby with heat problems? If not, why aren't
more folks concerned with light efficiency as opposed to how much light
can be squeezed over their tank?

--
A friend will help you move. A real friend will help you move a body.