Hi and welcome to the forum
What are the tank dimensions (length x width x height)?
How long has the tank been set up for?
Has the filter cycled?
What sort of filter is in/ on the aquarium?
How often and how do you clean the filter?
How often do you do water changes and how much do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?
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What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
Depending on what the GH of your water is, will determine what fish you should keep.
Angelfish, discus, most tetras, most barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.
Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.
If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH and keep fishes from softer water.
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HOW MANY OF EACH FISH
Most tetras (including flame and black tetras) should be kept in groups of at least 10 or more. These fishes naturally occur in groups consisting of thousands of individuals and even 10 is a small number for them.
Corydoras need to be in groups of at least 6 (preferably 10) or more. Again these fish naturally occur in groups of hundreds ad act more naturally when in groups.
Angelfish naturally live in groups but can be kept on their own if the tank is big enough. They can grow to 5 inches long and 6+ inches high. The smallest tank for a freshwater angelfish (Pterophyllum sp) is 3 ft long x 14 inches wide x 18 inches high.
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What species of Plecosotmus do you have?
Post a picture of it if you aren't sure.
The common pleco (Hypostomus plecostomus) can grow to 2 feet long and regularly hits 10-12 inches in the average aquarium. The gibbiceps pleco (Pterygoplichthys gibbiceps) is often sold as a pleco and can grow to 18 inches long, and it can also hit 10-12 inches in an average aquarium (bigger in a big aquarium). If it's a common bristlenose pleco (Ancistrus cirrhosus), then it grows to about 4 inches and should be fine in the tank.
All suckermouth catfish need driftwood and algae to help their digestion. They can have other types of food too but need access to wood and algae. You need to leave the tank lights on for long enough to grow algae on the glass and ornaments for these fish.
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FOOD FOR AQUARIUM FISH
The fish can be fed a variety of dry, frozen and live fish foods that can include the following. The pleco should have algae and wood in addition to other types of food like sinking pellets or algae wafers.
Dry foods can include flake, pellet and freeze dried foods. Freed dried foods should be soaked in water for a fed minutes before feeding.
Frozen foods can include things like brineshrimp, daphnia, mysis shrimp, bloodworms, marine mix (consists of prawn, fish & squid blended up), marine green mix (same as marine mix but with algae added). You can also use raw or cooked prawn/ shrimp that is kept frozen until needed. You can catch (without chemicals) and freeze small non-poisonous insects like ants, flies, moths, mosquitos, mozzie larvae, etc. You put them in a plastic bag or container and pop them in the freezer. Mozzie larvae and live daphnia can be put into ice cube trays with a small amount of water and frozen. Make sure nobody uses the ice blocks for their drinks.
*NB 1* If you have shrimp in the tank, use cooked prawn so you don't introduce diseases that kill the shrimp.
*NB 2* Some brands of bloodworms are irradiated by the company. That helps kill off the bad bacteria on them. Other brands are not irradiated. Try to get the irradiated brands because fish are less likely to develop intestinal infections from the irradiated brands.
*NB 3* Some people are allergic to bloodworms. If you have never used frozen bloodworms for fish food, rub a small amount of defrosted bloodworms on your finger and wait a couple of minutes. See if you get a rash or an itchy finger. If you do, then you have an allergy to them and should wash your hands with soapy water immediately, and avoid them or wear rubber gloves when handling them. Everyone should wash their hands with soapy water after handling frozen bloodworms or any frozen fish food.
Live foods can include brineshrimp (adult and newly hatched), daphnia, glass shrimp (for bigger fish), mosquito larvae, aphids, ants, small non-poisonous insects (flies, moths, etc) that are caught without chemicals, microworms, grindal worms, white worms, small earthworms.
If fish are vegetarian, you should avoid feeding them meat based foods and limit the bloodworms in their diet. You can grow algae on smooth rocks or ornaments outside in containers of water and bring the rock inside for a week so the fish can graze on it. After that time, you swap the rock for another one in the bucket so the fish have a steady supply of algae.
You can grow small floating plants like Duckweed in aquariums or outside in ponds/ tubs. A lot of vegetarian or omnivorous fishes with eat small soft leaf aquatic plants.
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LIGHTS FOR AQUARIUMS
TURNING LIGHTS ON AND OFF
Stress from tank lights coming on when the room is dark can be an issue. Fish don't have eyelids and don't tolerate going from complete dark to bright light (or vice versa) instantly.
In the morning open the curtains or turn the room light on at least 30 minutes (or more) before turning the tank light on. This will reduce the stress on the fish and they won't go from a dark tank to a bright tank instantly.
At night turn the room light on and then turn the tank light off. Wait at least 30 minutes (or more) before turning the room light out. This allows the fish to settle down for the night instead of going from a brightly lit tank to complete darkness instantly.
Try to have the lights on at the same time each day. Use a timer if possible.
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TWO LIGHT UNITS
If you have two light units on the tank, put them on timers and have one come on first, then an hour later the second one can come on. It will be less stressful for the fish.
In the evening, turn the first light off and wait an hour, then have the second light go out.
If the lights have a low, medium and high intensity setting, have them on low in the morning, then increase it to medium after a couple of hours, and then high for the main part of the day. In the evening, reverse this and have the medium setting for a few hours, then low. Then turn the lights off.
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LIGHTING TIMES
Most aquarium plants like a bit of light and if you only have the light on for a couple of hours a day, they struggle. If the light doesn't have a high enough wattage they also struggle. Try having the tank lights on for 10-12 hours a day.
If you get lots of green algae then reduce the light by an hour a day and monitor the algae over the next 2 weeks.
If you don't get any green algae on the glass then increase the lighting period by an hour and monitor it.
If you get a small amount of algae then the lighting time is about right.
Some plants will close their leaves up when they have had sufficient light. Ambulia, Hygrophilas and a few others close their top set of leaves first, then the next set and so on down the stem. When you see this happening, wait an hour after the leaves have closed up against the stem and then turn lights off. It's worth investing in a couple of these plants just to see how they do. They are generally good in most aquariums and give you a rough idea of if you have enough light on the tank.
Plant lights should have equal amount of red and blue light and a bit less green light.
