12-08-2010, 06:02 PM
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First on the otos and feeding: unless you have out-of-control algae, there will not be sufficient algae long-term in a 5g to keep 2 otos fed and healthy. Fortunately, they become very used to sinking foods once they are settled in a new home; having algae at first is very wise, otherwise they may well starve. But when they have eaten most of it, they will look elsewhere. Mine regularly appear at feeding time with the corys and other substrate fish and eagerly await the tablets, pellets, etc. Make sure you have some vegetable ones, like spirulina or algae; they will eat other types too but veggie food is good for all fish and esp these.
Otos will only eat common green algae (you will hardly see this, they are so good at getting it) and diatoms (the brown common in new tanks). The green dots on the glass is likely green dot or spot algae. Some larger pleco are said to eat it, but generally it needs to be removed by you. A solid (hard) scraper is needed. If you catch it before you can even really see it, it is much easier to control. I run a stiff sponge on a stick over the front glass every week during the water change, whether I see anything or not; if I don't, sure enough by next week there will be a couple green dots. It occurs in some tanks but not others.
Nitrates should be kept low; any rise in nitrates is a signal something is not balanced. While there is some difference of opinion on the exact numbers, by far the majority of aquarists and authors suggest never letting nitrates rise above 20ppm, although up to 40ppm is held by some. One thing is certain, nitrates are not appreciated by fish, whatever the sensitivity of individual species may be (and they vary a lot, some cannot tolerate nitrates above 10ppm without severe stress, others much higher). So keeping them low is always advisable. The weekly partial water change does this. So do live plants. In well planted tanks, nitrates are frequently zero or at most 5-10 ppm, depending upon the source water, plants, and fish load.
One last addition on the benefit of water changes: fish excrete "crud" which includes waste (solid and liquid) and pheromones. There is absolutely no way to remove all this except either live plants (a lot and few fish to balance) or water changes. Filters move water around, and bacteria break down solid into liquid--but they don't remove it. Plants can if the fish load is very minimal, far less than most of us have. I have well-planted tanks, but I still change 50% of the water in all my tanks every week, and have done for more than 15 years. Doing a water change only when nitrates increase is letting it go beyond the safe point; water stability is the goal, and this is achieved with regular substantial water changes--and l;ive plants help us in stable water--and that is healthier for the fish.
Last edited by Byron; 12-08-2010 at 06:05 PM..