pushing the limits of a 10 gallon

Question
Hi.  I'm sorry to send a long question, but here it goes.  We got my 4 yr old daughter a 5 gallon aquarium which quickly became overstocked and an incredible amount of work(we should have researched before we jumped in). We found a local fish store that sold us a used 10 gallon set up.  We have 2 zebra danios, 1 glofish, 1 neon tetra, 2 platys (1m 1f), 2 mystery snails, and 3 ghost shrimp.  The person I've been dealing with says that hes been keeping danios and platys for years, and from his experience he counts danios as 1/2 inch per gallon instead of the 1" per gallon I keep reading about.  He's recommended adding 1-2 more danios to keep them happy and one more female platy to keep the platys happy because the male wont give the female a break.  He swears up and down that the tank will support it with bi-weekly or even monthly water changes because these fish don't have as much bio-load as some others.  Being that its my daughters tank and she loves watching them I love this idea.  All of these fish were in the 5 gallon and it looked great with all of the action, now in the 10 gallon it looks kinda empty.   The new setup is 10 gallon tank with a 50 watt heater and an aquaclear filter for up to thirty gallons.  I used all of the water and gravel from the five gallon when we made the switch, and we haven't lost any fish.  Its been one week and the ammonia reads zero with low nitrites (had it tested at petsmart).  I really would love to be able to add another platy and 1-2 more glofish (they are danios, right?) because my little girl would love it, but I'm afraid that, being new to this, we'll end up with a tank that kills fish and is constant maintenance.  I don't mind pushing the limit, I just don't want to break it. Any advice you could give this rookie fishkeeper would be greatly appreciated.  Thank you in advance.

Answer
Hi Jason,

Well, I can give you some great advice, but I ask one thing:  Please don't shoot the messenger if it's not the advice you're looking for. :)  I'm very honest and I don't want to advise you incorrectly, but sometimes that goes over like a lead balloon and because I don't recommend housing more fish, someone gets mad and I get a horrid rating, lol.  I don't need bad ratings.  In fact, I quite adore 10s!  I work hard here, and it is on a voluntary basis.

With that said, here is my advice:

Local fish store employees (as is common, even owners give bad advice in order to make $) and give the worst advice possible.  1/2" per gallon?  NO.  

1" per gallon.  2" fish = 2 gallons each, but with low exhuders, we can go with 1.5g/2".

You have 2 zebra danios, one glofish, one tetra, 2 platties.  Mystery snails and ghost shrimp are considered "invertibrates" and they do not count as fish.  They are cleaners, not heavy exhuders.

2 zebra danios (which I also raise) = 2 - 3 gallons
1 glofish =  1 gallon
1 tetra = 1 gallon
2 platties = 2 gallons

Your lowest total gallons = 6 gallons.  
Your highest total gallons (when danios are grown) are 7 gallons.

You may add 2 more Danio, and because you run a 30 gallon filter and do bi-weekly water changes, you can add 2, but (BUT), keep up with the water changes and make sure that you replace the filter media monthly.

You might consider adding tetra rather than danios.  Tetra are also school-oriented fish.

I raise and keep both Neon Tetras and Zebra/Leopard/Lace Danios.  :)

Here is a neat video of my fish breeding.  Your daughter might really love this.

http://www.youtube.com/watch?v=6XCGxhPZ-T8

I hope this is helpful for you and that it answers your questions professionally.

Additionally, I hope you like the video! :)

Happy fish-keeping.
Renee