water changes and filter frequencies

Question
QUESTION: Hi Nathan,

  This is a great hobby - very enjoyable. I have a 75 gallon tank filled with platys and tetras (50) and 7 albino cory catfish. I test the water frequently and it shows no ammonia at all but haven`t procured test kits yet for nitrites and nitrates.I was taking 1 gallon of water out and putting 1 gallon of water in  with 1 teaspoon of uniodized saly daily thus keeping the water pretty clear. Do I need to do a water change of 33% about once every 3 weeks or should I just keep the gallon ritual up daily which is no trouble? If you say I need to change the water please tell me why. Also how often should I clean the filter. It is an Aqua Clear 110 and seems to do a good job.

ANSWER: Hi Jeffrey,

First of all, you have a bit too many fish in there, but as long as your fish don't reproduce, and you have a good maintenance routine, your fish should be fine. (The Tetras will probably eat any babies the Platies produce, you you probably won't have to worry about overpopulation.)

Your routine of a gallon daily is good, but switching to 5 gallons twice a week would be better. (It would be easier for you, too!) Your fish don't need salt, the only freshwater fish that requires a small amount would be the Molly. It won't really affect the fish too much. Aquarium salt is mainly used in conjunction with disease treatment.

You need the regular water changes to help dilute the toxins that inevitably form in the aquarium environment. An aquarium is a closed system, unlike a river or ocean, so water changes are necessary.

So, once again, 5 gallons twice a week, plus a filter media change (the foam and carbon, but not the BioMax) once a month. This would be the ideal routine.

Good Luck, and Happy Fishkeeping!

---------- FOLLOW-UP ----------

QUESTION: Just one more thought - How do you feel about doing just one (1) 30% waterchange every three weeks and cleaning the filter at that time also and thus eliminate the 5 gallons water change weekly. Would this be sufficient to keep the fish healthy? Of course this would be easier on me but that`s not what I`m after. Also one other thought: I currently feed the fish twice a day, once with flakes and the other with frozen blood worms and some flakes for variety and good health. How much in quantity do you give them? Remember I have 57 in total. It seems they can never stop eating and come to you as you look at them to get more food at any time of the day. The American children are obese but I don`t want my fish the same way. I don`t want to over feed them as this will shorten their lives and probly produce more ammonia, nitrites and nitrates etc. in the tank. Currently they look well fed and maybe a bit fat I`m sure.

Answer
Hi Jeffrey,

It's best if you were able to perform approximately 10% water change per week. (Approximately 7 gallons in your case) Large water changes infrequently can stress the beneficial bacteria residing in the tank. As a general rule, no more than 25% of the water should be changed at a time, except in the case of disease treatment, etc. If you really wanted, you could do your 30% water change, but it would be best to do the weekly 10% water changes.

If you are going to do the 10% water changes weekly, a gravel vacuum once per two changes would be great.

You should feed them as much as they can consume in one to two minutes. I put in a handful, then stop, and wait for them to eat it all. Then, I put in another small handful and wait for them to eat it. When about a minute or two is up, I stop. See if they are dashing to the food and gobbling it up quickly. If they are a bit slow getting to the food, or if they eat it, spit it out, and eat it, etc, then you may already be feeding enough.

Your fish sound healthy to me, I think your feeding routine is good already.

Good luck, and happy fishkeeping!