Hey Brian,
A 10G will make a lovely setup, but when having more than 1 dp there is always a chance they will not get along when getting older. For this reason, I recommend making sure you will always have a 5G on hand which you can move 1 into if you have to. That said, lets start!
A 10G will be able to keep 2 dwarf puffers, I wouldnt go for 3. The rule tends to be 5Gallons per puffer, and it's not a rule that stretches easily. Puffers prefer sand, and dark sand at that. Sand is a must, dark is a preference (they'll prefer, but won't need), gravel tends to be too sharp and pointy seeing as puffers often sleep on the bottom and sometimes even burry themselfs in the substrate. An inch of sand should do, but I prefer using about 2 inches seeing as this will hold the roots of plants better.
So I'd say, get rid of the gravel (keep some in tights for now, so the tank will be pretty much cycled right away, and you can remove it after about 2 weeks*) and get sand. The filter I'd keep the way it is so you wont go through a full cycle. The water is up to you, there's not much benificial in it.
The tank will have to be well planted, to break up the eye sight of the puffers. They'll need to be able to get away from eachother quickly when they want to. When puffers are young they tend to group and stay together, when they age the get aggressive towards eachother. For breaking up the eye sight it's best to use a combination of rocks/wood & plants. Terracota pots can be used too, but look less natural
The tank will also have to be heated and well filtered. Puffers are messy easters, so yeah
Thats the setup pretty much done.
Looking after dwarf puffers isnt too difficult really, even though them getting along comes down to luck. I recommend getting 1 male and 1 female or 2 females. The males dont tend to get along too well, or rather ... chances of fights leading to death seem to be higher in m/m ratios rather than f/f or m/f. They'll still not get along too well though
You can see the difference by having a close look at them. Males will have a dark line showing on their belly (though I have noticed this sometimes fades.. females however, will never have it), and they will have wrinkles behind their eyes (these will always show). Buy them at the same time, and put them in at the same time. Once 1 has formed a territory already it will wound if not kill all others that enter. For this reason it's not recommended getting a puffer later on and adding them 1 by 1 over a long period of time.
Frequent water changes should be done, seeing as they're quite sensitive to ammonia. Once a week, 30% should do the tick in a well filtered 10G though.
Feeding:
Bloodworms are best used as a main source of food, feed them this once every 2 days. Make sure to not feed too much though, seeing as often puffers only eat that what moves. Meaning that as soon as it leaves the current of the filter and touches the bottom, it will be ignored. You can see the belly grow and it's not that difficult to tell when you've fed them enough
Make sure not too many bloodworms stay left behind on the bottom, it will pollute the water. Untill you've figured out how much to feed, I recommend getting rid of the bloodworms that stay left behind right after the feeding.
You can vary their diet by giving them live or frozen foods. Mine seem to ignore pretty much everything though
Things to try out as treats are: daphnia (live or frozen), white musquito larvae, brine shrimp (if live, make sure to rinse them under fresh water first to get rid of the salt on them), mysis shrimp, river shrimp (live or frozen), cut up mussels etc!
A must in feeding though, is snails. All snails cept for malasian trumpet snails (their snails are too hard and are likely to break the puffers teeth rather than trim them). The golden rule is "it will get crushed as long as its smaller than the size of the puffers eye". You can imagine that the snails need to be quite small
Larger ones can be used as treats however. The puffer will simply bite of their heads or try and suck them out of their shell. The shell will have to be removed afterwards, seeing as the dead snail inside will start rotting and pollute the water.
*Gravel keeping:
The substrate contains must benificial bacteria, so if you keep the gravel you'll have an instant cycle. However, you want to move onto sand for the puffers. I recommend scooping out the gravel but rather than throwing it away, putting it into tights (stockings, panty-hose, whatever you wanna call it
) Tie up the ends of it, and put it onto the sand. This way the bacteria will quickly grow and move into the sand as well, causing an nearly instant cycle rather than having to start all over again. In about two weeks you can remove the gravel & tights and have a fully cycled tank.
--Edit--
About the ottos as clean-up crew. Keep a very close eye on them, some people manage to pull it off, others end up having an otto missing an eye or even dead.
Also have a look at
Topic about dwarf puffer setup and
Puffers are not community fish for some more information (Even though the last post is not about DPs, the same still goes for them).
I think that's all ... if any more questions, I'd be happy to answer them
