clean water

Question
Hi Wayne
need some tips on how to keep water crystal clear please, 3ft tank with 16 various fish,  2 angels, 1 silver shark 4in long, 2 redeyes, 1 plec, few others, thanks

Answer
Hi, John, A 3ft tank is about 20-37 gallons depending on how tall. First you didn't send much info but I'll work w/o that. Since you have Angels I assume the 16 various ones are on the small side. There is a long stood by rule of 1" of fish per gallon. That is a good rule to go by but if you "over filter" the tank it can stand crowds. That said I think you are at the limit on numbers.
   Tips: Ph is the most important thing to check. Most tropicals will be fine with a PH slightly acid of 6.0-7.2. Below 5 you invite trouble. I never worry about a high PH as it goes down naturally from fish waste etc.
   Actual live plants will help clear the bad elements. Keeping them alive takes practice. 10 hours of light/ day. Remember that when the tank is dark plants reverse their process and take IN Oxygen and give off CO2. The CO2 drops fast when you turn light on.
   If you have hard water here is an easy way to soften it.....cut the toe out of you ladies nylon hosery. Put in 2 tablespoons of Sea Salt (for 30 gals). Hang that at the outflow of your filter.
    Filtration....Whatever style filter you have can be improved. To start with, if you have one of those filters that sit on the bottom in the corner then get rid of it. I prefer the canaster type because they simply clean better. However, most people have the overflow types that hang on the outside. The problem is that the intake tubes on those are always located right where the clean water goes back in. That never made sense to me. Why keep sucking in the same water? The water far away from the intake never gets filtered. UNLESS you have a power head to circulate the water better, the tank gets little mixture. Heres how to improve them:
    You can get a power head that circulates the water. Set that on the opposite end of the tank that the filter is on.
     OR
   Extend the intake tube across the bottom. This takes some trial and error but it works great. Lets take your 36" tank. Set the filter on one END, not on the back. Before you do that you will have to check the hood to see how you are going to fit it around the filter. You may be able to cut the hood you have to fit around the end mounted filter. No hoods are designed for an END MOUNTED filter. For that reason I get plexiglass and cut my own top to fit around it. There are special blades for a sabre saw to cut plexiglass with. And carbide drill bits to drill holes for air tubes.  A nice looking light sits on that. Ok so you got the filter on the one end and the top all set. Take the intake tube with you to your nearest fish store. Yes, that guy that deals mostly in fish not everything else. OMG not PetSmart!!!
 Buy the following:
  1 piece hard plastic tubing, 36" long, the same diameter as your intake,
  2 couplings that will connect the 2 together,
  1 of those clear square fittings that fit on the top of the stand tubes on an undergravel filter. You just want the square end piece.
  1 carbon cartidge that fits in the above square fitting.

Back at home.
>>>>Light a candle.
>>>>Measure from the lower end of the present intake to the tank bottom.
>>>>Heat the 36" tube slightly until it will bend at that point. Leave just enough on the short end so it will extend from the bottom up to where the regular intake ends. If its too long you can cut some off. It works better if you bend it in 45 degrees twice (an inch apart) rather than 90 degrees all in one place. The tube will flatten some but will work fine. This takes some practice not to get it too hot. Clear hose will NOT stay bent.
>>>>Now you have a 36"tube with an elbow on one end.
>>>>Insert the square fitting with carbon catridge onto the long end.
>>>>Remove the top. Shut off the filter. Set the new tube on the bottom so it goes all the way across to the opposite end. Using the coupling make sure the elbow end will fit onto the verticle intake, then hook those together. Cover that with the gravel leaving the carbon cartidge barely above the gravel.
   What you get is the filter removing water from the bottom of one end and putting it back on the top of the other end. You will get much better filtration. The carbon cartridge is not required but I've found that fish seem to love swimming into that square hole and get stuck. So the cartridge prevents that. Whenever you need to take the filter off the tank remember to put one hand below the coupling to hold it down and put up on the standard intake so you don't move the bottom buried tube.
  If you get a canaster filter it is easier. You can go to Lowes or H.D. and get clear hose at the horrid cost of 2 miles for $1 and extend the normal hoses so it intakes from one end of the tank and out the other. My fish store guy has me as an "on call" set up person. I am currently setting up a 300 gallon in a doctors office using this method and 2 canaster filters.
So maybe you don't want to go to that extent. I assume you use those blue/white filter cartridges with carbon inside. The amount of carbon in those isn't enough to filter a cup off coffee much less a tank. The more of them you buy the more profit someone gets.
  TIP:: go buy 3 sets of those blue/white cartridges that just slide right in your overflow filter. Also buy the biggest can of activated charcoal you can find. I get mine in 50 pound bags for $25. Carefully cut a small hole along the top off the blue material and spoon into where the charcoal is as much charcoal as will fit. Put those back in. Weekly rinse the gunk from the outside, dump out the charcoal and spoon in new. Use each cartridge until the gunk will not rinse out.
   Chrystal Clear? No tank is totally clear. You should be able to see through it from end to end. But its never clear as if "nothing" was there. Vacuuming the gravel monthly is a good idea. You need to do water changes anyway so may as well get that gravel vacuum thing. I assume you know how those work. There are water change devices that connect to the kitchen faucet. They have 2 hoses. Push the lever one way it sucks water out of the tank. The other way puts it back from the tap. Well worth the $50 price at Pets Smart. $45 at Wally World. I have yet to find anything at Lowes to make it cheaper to make one.
  Vacuum you gravel monthly and get more charcoal in the works. It'll be fine.