Mainteinance suggestions on a saltwater tank.?

Question

I have a 20 gallon saltwater tank and I have the following problems:
1. The only fish I can keep in it are damsels all others die off rather quickly. Damsels last me anywhere from 6 months to 1.5 years. Is that a normal life for damsels?
2. Hermit crabs for some reason even if I feed them pellets and even if they get plenty of algae once they get past a certain size they die off. I had suggestions that its because of lack of shells but, literally, my whole aquarium floor has empty shells to choose from.
3. I currently have just a normal filter on it and clean the tank/change about 2-3 gallons of water once a week. Any suggestions on what other types of equipment I could use for such a small tank? Uv sterylizers and protein skimmers always seem to be made only for larger tanks.
I'd ideally want to make my aquarium self sufficient me only needing to change water but Ive had it for years and I never get the right setup.

Answer 1

1.Damselfishes are easy to keep in aquaria; they are not fussy in terms of water chemistry and physics. Temperatures in the low to upper 79's degree F. (79-82) are ideal. Most tolerate and enjoy a wide range of salinities. The industry usually keeps theirs in a specific gravity of @ 1.024-1.026 to decrease salt mix costs, increase gas solubility, reduce algae growth and curtail epizootic outbreaks. Damselfishes are parasitized internally and externally by several species of sporozoans, Cryptocaryon, Oodinium, roundworms, flukes tapeworms and crustaceans. Depending on the water chemistry parasitic signs and reproduction will occur. They are usually agents and transmitters of diseases.

2. Most marine hermit crabs will appreciate a salinity of between 1.023 and 1.025 (measured in specific gravity), and temperatures between 4–14°C (temperate species) and 24–27°C (tropical species), with a good bed, algae to graze on and a variety of shells to change into.
Hermit crabs require iodine calicum and other trace elements to live healthy. What type of lighting do you have??
Prefferable: Power Compact
Kent products:
Calcium
Micro-Vert
Iodiine
Phytoplex
Coral- Accel
Trace Elements


3. Hang-on-tank canister filters are very often only used as a means of mechanical filtration during regular tank cleaning and maintenance care routines. They are also one of the simpliest ways to control heavy copepod and amphipod larval blooms. I have a Magnum diatomite 360 filter and works perfectly.
Protein skimmers are a good source in removing chemical waste and harmuful chemicals. I will recommend buying one.
Uv. sterelyzers are most commonly used in reef setups.

Other:
1. Temp=?? --- Ideal 79-82
2.Salinity=??--- Ideal 1.024-1.026
3. Ph=??--------- Ideal 8.2
4. Ammonia=??Ideal 0ppm
5. Nitrite =?? -- Ideal 0ppm
6.Nitrate=?? -- Lowest possible

What are your readings? Do you have a testing kit?
Hope this helped.

Answer 2

I have a 20 g also I have had it for 6 months now, I will explain my set-up, I have a Marineland Penguin 200, a maxi-jet 400. Small heater tetra I believe. 35 lbs of live sand, 3 lbs. of live rock. I have two ocellaris clowns, 4 hermit crabs, 1 sand sifting sea star. I lost one hermit crab, also when you see them on the bottom out of the shell, that may be there exoskeleton since the shed then molt to grow. SO they will show up sooner or later. I had a Flame Angel but it died due to a parasite. Not too sure if this helps but it has been quite successful for me.
EDIT: I also change 2 gallons weekly, and have never had a water parameter problem, also add freshwater daily to keep salinity correct (not that you did not already know that!)

Answer 3

Before trying a lot of new equipment (that may or may not solve the problem you're having), do you know the ammonia, nitrite, nitrate, pH, and salinity levels in your tank? More problems are related to improper water quality than anything, and if you can give us these results, we might be able to narrow down the cause of your deaths. If you know this information, you can add it here by using the pencil icon under the question to "Add Details".

NOTE: Damsels should have a life span of about 5+ years. If the fish are wild-caught, you don't know the age when you get them, but they should live longer than 1-2 years.

Answer 4

Dump the canister filter and buy a hob (hang on back skimmer)if you don't have a sump.20 gallons is very small for a marine tank and not very forgiving if your water parameters go astray.Are you checking your ammonia and nitrate levels?
Do you have any copper at all in your system?It will kill all invertibrates quicksmart.Try the reefcentral forums.Heaps of help there. :)