I have a few comments/suggestions to add to what others have posted on the following specifics.
Can you dose too much prime? I'm not saying the whole bottle, but is it more beneficial to try to be exact or can you triple dose with no side effects?
As Nick set out in post #6, there is a danger to overdosing Prime. But aside from that issue, any additive in the tank water is getting inside the fish, and the fish must somehow deal with these. Conditioners (any brand), plant additives (liquid), medications, etc all end up inside the fish, in the bloodstream and organs. Even those that are not immediately toxic to kill the fish will cause the fish stress in dealing with them, so keeping these to the absolute minimum is always advisable. Think of it like human medicine...overdosing is usually more harmful than beneficial. Same holds for any additives to fish tank water.
Initially, when I first started the tank I was injecting CO2, but now the tank is fully stocked, maybe even overstocked. For the guys with heavily stocked tanks, both fish and plants, do you inject CO2? I may stop after that one day my fish were breathing heavy, maybe now they will be producing enough CO2 on their own. Not using it now due to the ick but in about 2 weeks time.
There is more naturally-occurring CO2 in the normal aquarium than many assume. While fish, plant and some bacteria respiration does create some of this, the majority is from the decomposition of organics in the substrate [one reason why a substrate is so important]. Unless you are running an "aquatic garden" high-tech planted tank with mega lighting and daily nutrient supplementation, adding diffused CO2 is not going to help the plants because it will not be in balance with the light intensity and other nutrients. My tanks are all planted, including floating plants, and I have never used any form of artificial/added CO2. Like the above issue, here too the less stuff entering the water the safer and healthier the fish are likely to be.
Lighting drives plant photosynthesis, and different plant species have varying requirements according primarily to their growth habit. Find plants that do well (= grow) under your lighting, then ensure the basic nutrients are sufficient to provide what the plants need to make use of that light.
Due to the heavy stock, I want to start doing 50 percent water changes per week, my issue is its currently being done manually with a 5-gallon bucket. I have attached 2 photos of the sinks nearby, has anyone been successful attaching a vaccum hose to one of these ends?
What I did was to install a basic faucet on my laundry sink; this is a faucet with threads much like the outside taps, so that a hose (or the Python) can be attached. It might mean a longer series of hoses, depending where the sink is located relative to the aquarium(s).
The faucet attachment with the Python is not particularly well made; I have gone through a couple of them, and found the Aqueon brand much more reliable. Same concept, and can be attached to an existing Python hose.
Last question, any tips on feeding bottom dwellers blood worms or brine shrimp? The food usually doesn't make it down due to all the other fish.
I feed bloodworms once a week as a "treat" a couple hours after the water change. Using a pipette that you can make from a short piece of stiff tube and a longer piece of air tubing, is my method; a baster utensil also works. Thaw the frozen food (never add frozen food to a fish tank anyway) in a dish of warm water, then use either implement to squirt the food down at the substrate level.